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Phenolphthalein is used as a laboratory reagent and acid-base indicator and in over-the-counter laxative preparations. The National Cancer Institute nominated phenolphthalein for study because of its widespread use as a component in numerous laxative preparations and the lack of adequate testing for carcinogenicity in experimental animals. Male and female F344/N rats and B6C3F1 mice were exposed to phenolphthalein (98% to 99% pure) in feed for 14 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood. 14-DAY STUDY IN RATS: Groups of five male and five female F344/N rats were given 0, 6,250, 12,500, 25,000, 50,000, or 100,000 ppm phenolphthalein in feed for 14 days. All rats survived to the end of the study. The final mean body weights of all exposed groups of rats were similar to those of the controls. No chemical-related gross or microscopic lesions were observed. 14-DAY STUDY IN MICE: Groups of five male and five female B6C3F1 mice were given 0, 6,250, 12,500, 25,000, 50,000, or 100,000 ppm phenolphthalein in feed for 14 days. All mice survived to the end of the study. The final mean body weights of all exposed groups of mice were similar to those of the controls. No chemical-related gross or microscopic lesions were observed. 13-WEEK STUDY IN RATS: Groups of 10 male and 9 or 10 female F344/N rats were given 0, 3,000, 6,000, 12,000, 25,000, or 50,000 ppm phenolphthalein (equivalent to average daily doses of approximately 200, 400, 800, 1,600, or 3,500 mg phenolphthalein/kg body weight to males and 200, 400, 800, 1,700, or 3,600 mg/kg to females) in feed for 13 weeks. Additional groups of 10 male and 10 female rats designated for clinical pathology evaluations were also given 0, 3,000, 6,000, 12,000, 25,000, or 50,000 ppm phenolphthalein in feed until day 21. All core study rats survived to the end of the study. The final mean body weight of the 50,000 ppm females and the body weight gains of the 25,000 and 50,000 ppm females were significantly lower than those of the controls. The final mean body weights and mean body weight gains of all other exposed groups were similar to those of the controls. There was no cathartic action or any other clinical finding attributed to exposure to phenolphthalein. The few differences in the hematology and clinical chemistry parameters were sporadic and were not considered to be chemical related. The percentage of motile sperm in the 12,000 ppm males was significantly greater than that in the controls, but no other significant differences in sperm morphology or vaginal cytology between exposed and control groups were observed. Absolute and relative liver weights of 25,000 and 50,000 ppm males were significantly greater than those of the controls. No chemical-related gross or microscopic lesions were observed. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were given 0, 3,000, 6,000, 12,000, 25,000, or 50,000 ppm phenolphthalein (equivalent to average daily doses of approximately 500, 1,000, 2,000, 4,100, or 9,000 mg phenolphthalein/kg body weight to males and 600, 1,200, 2,400, 5,000, or 10,500 mg/kg to females) in feed for 13 weeks. All mice survived until the end of the study. The final mean body weights and mean body weight gains of all exposed groups were similar to those of the controls. There was no cathartic action or any other clinical finding attributed to exposure to phenolphthalein. The absolute right cauda weight of the 12,000 ppm males and the absolute right epididymis weights of 12,000, 25,000, and 50,000 ppm males were significantly less than those of the controls. The percentages of abnormal sperm in 12,000, 25,000, and 50,000 ppm males were significantly greater than that in the control group, and the sperm concentrations in 12,000 and 50,000 ppm males were significantly less than that of the control group. The absolute and relative right testis weights of males exposed to 6,000 ppm or greater and the absolute right testis weight of 3,000 ppm mof 3,000 ppm males were significantly less than those of the controls. The incidences of hypoplasia of the bone marrow in males and females exposed to 12,000 ppm or greater were significantly greater than those in the controls. The incidences of hematopoiesis of the spleen in 25,000 and 50,000 ppm males were significantly greater than that in the controls. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were given 0, 12,000, 25,000, or 50,000 ppm phenolphthalein (equivalent to average daily doses of approximately 500, 1,000, or 2,000 mg phenolphthalein/kg body weight to males and 500, 1,000, or 2,500 mg/kg to females) in feed for 2 years. Survival, Body Weights, and Clinical Findings: Survival of exposed males and females was similar to that of the controls. The mean body weights of exposed males were less than those of the controls through most of the second year of the study, and the mean body weights of exposed females were less than those of the controls from about week 16 until the end of the study. Clinical findings attributed to phenolphthalein exposure included thin appearance and ruffled fur in all exposed groups of males. Determinations of Total Phenolphthalein in Plasma: The mean plasma concentrations of total phenolphthalein (free and conjugated) after 2 years of exposure varied little with time of day. Plasma concentrations of total phenolphthalein were approximately the same between exposure groups and between males and females. Pathology Findings: The incidences of benign pheochromocytoma of the adrenal medulla in all exposed groups of males were significantly greater than those in the controls and occurred with a significant positive trend. The incidences of benign pheochromocytoma in 12,000 ppm females and of benign or malignant pheochromocytoma (combined) in 12,000 and 25,000 ppm females were significantly greater than those in the controls. The numbers of exposed males with bilateral benign pheochromocytomas exceeded the number of controls with these neoplasms. The incidences of malignant pheochromocytomas in exposed rats were similar to those in the controls. The incidences of focal hyperplasia of the adrenal medulla in the 12,000 and 50,000 ppm males were significantly greater than in the controls. The incidences of renal tubule adenoma in 50,000 ppm male rats and of renal tubule adenoma or carcinoma (combined) in 12,000 and 50,000 ppm male rats were significantly greater than those in the controls. Although the increased incidences were predominantly of renal tubule adenoma, four carcinomas were observed in exposed males (0 ppm, 0/50; 12,000 ppm, 1/50; 25,000 ppm, 1/50; 50,000 ppm, 2/50). The incidences of renal tubule neoplasms in exposed groups of females were similar to those in the controls. The findings from an extended evaluation (step section) of the kidneys of female rats were similar to those from the standard evaluation. The incidences of nephropathy in all exposed groups of females were significantly greater than in the controls, and the severity of nephropathy in all exposed groups of males and in 25,000 and 50,000 ppm females was significantly greater than in the controls. The incidences of diffuse hyperplasia of the parathyroid gland (0/41, 16/48, 14/49, 14/46), fibrous osteodystrophy of the bone (0/50, 17/50, 14/50, 12/50), and mineralization (0/50, 11/50, 5/50, 5/49) and degeneration (0/50, 11/50, 5/50, 4/49) of the glandular stomach in exposed groups of males were generally significantly greater than those in the controls. The incidences of hyperplasia of the thyroid gland C-cells (13/50, 3/50, 9/49, 4/49) in 12,000 and 50,000 ppm males were significantly less than in the controls. These lesions are commonly observed in male rats with more advanced nephropathy and are considered to be associated with a calcium/phosphorus imbalance created by compromised functional capacity of the kidney. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were given 0, 3,000, 6,000, or 12,000 ppm phenolphthalein (equivalent to average daily doses of approximately 300, 600, or 1,200 mg phenolphthalein/kg body weight to males and 400, 800, or 1,500 mg/kg to females) in feed for 2 years. Survival, Body Weights, and Clinical Findings: Survival of the 12,000 ppm females was significantly lower than that of the controls; survival of all other exposed groups of mice was similar to that of the controls. The mean body weights of 12,000 ppm males were slightly less than those of the controls beginning at week 93 of the study, and the mean body weights of the 3,000, 6,000, and 12,000 ppm females were less than those of the controls during most of the second year of the study. In exposed mice, there were no clinical findings related to phenolphthalein exposure. Determinations of Total Phenolphthalein in Plasma: The mean plasma concentrations of total phenolphthalein (free and conjugated) after 2 years of exposure varied little with time of day. Plasma concentrations of total phenolphthalein were approximately the same between exposure groups and between males and females. Pathology Findings: The incidences of histiocytic sarcoma in 6,000 and 12,000 ppm males and females were significantly greater than those in the controls and occurred with a significant positive trend. In this study, histiocytic sarcoma was consistently observed in the liver with several other sites (e.g., spleen, lung, bone marrow, and various lymph nodes) involved less frequently. The incidences of all types of malignant lymphoma and of lymphoma of thymic origin in all exposed groups of females were significantly greater than those in the controls and occurred with significant positive trends, while the incidences of all types of malignant lymphoma in all exposed groups of males were similar to that in the controls. The incidences of lymphoma of thymic origin were increased in exposed groups of males, but were significantly increased only in the 6,000 ppm group. The incidences of atypical hyperplasia of the thymus in 6,000 and 12,000 ppm males and in all exposed groups of females were significantly greater than those in the controls. The incidences of benign sex-cord stromal tumors of the ovary in all exposed groups of females were significantly greater than in the controls. The incidences of hyperplasia of the ovary in 3,000 and 12,000 ppm females were significantly greater than in the controls. The incidences of germinal epithelial degeneration of the testis in all exposed groups of males were significantly greater than that in the controls. There were increased incidences of myelofibrosis of the bone marrow in 12,000 ppm males (0 ppm, 3/50; 3,000 ppm, 8/50; 6,000 ppm, 8/50; 12,000 ppm, 19/49) and an increased severity but not incidence of this lesion in exposed females. There were also increased incidences of pigmentation of minimal to mild severity in the bone marrow of 6,000 and 12,000 ppm males (0/50, 2/50, 5/50, 16/49) and females (2/50, 3/50, 11/50, 11/50). Also, the incidences of hematopoietic cell proliferation in the red pulp of the spleen (10/50, 22/50, 28/50, 21/49) in all exposed groups of males were significantly greater than that in the controls, and the severity of this lesion increased with increasing exposure concentration. The incidences of hepatocellular adenoma in all exposed groups of males and females and of hepatocellular adenoma or carcinoma (combined) in 6,000 and 12,000 ppm males and all exposed groups of females were significantly less than those in the controls, and these lesions occurred with significant negative trends. Multiple hepatocellular adenomas were observed more frequently in the control groups than in the exposed groups. The incidences of clear cell and eosinophilic foci in all exposed groups of males and of mixed cell foci in 12,000 ppm males were significantly less than those in the controls. The incidences of eosinophilic foci in exposed groups of females were significantly less than that in the controls. GENETIC TOXICOLOGY: Phenolphthalein, tested in two laboratories, was not mutagenic in any of four strains of Salmonella typhimurium with or without S9 metabolic activation enzymes, and no induction of sister chromatid exchanges was observed in cultured Chinese hamster ovary cells treated with phenolphthalein with or without S9. However, significant increases in chromosomal aberrations were observed after treatment of cultured Chinese hamster ovary cells with phenolphthalein in the presence of S9, and the frequencies of micronucleated erythrocytes were increased in peripheral blood samples from male and female mice administered phenolphthalein in feed for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was clear evidence of carcinogenic activity of phenolphthalein in male F344/N rats based on markedly increased incidences of benign pheochromocytomas of the adrenal medulla and of renal tubule adenomas and adenomas or carcinomas (combined). There was some evidence of carcinogenic activity of phenolphthalein in female F344/N rats based on the increased incidences of benign pheochromocytomas of the adrenal medulla in the 12,000 ppm group and of benign or malignant pheochromocytomas (combined) in the 12,000 and 25,000 ppm groups. There was clear evidence of carcinogenic activity of phenolphthalein in male B6C3F1 mice based on increased incidences of histiocytic sarcomas and of malignant lymphomas of thymic origin. There was clear evidence of carcinogenic activity of phenolphthalein in female B6C3F1 mice based on increased incidences of histiocytic sarcomas, malignant lymphomas of all types, lymphomas of thymic origin, and benign sex-cord stromal tumors of the ovary. Exposure of rats to phenolphthalein in feed for 2 years resulted in increased incidences of focal hyperplasia of the adrenal medulla in males and in increased incidences and/or severity of nephropathy of the kidney in males and females. Exposure of mice to phenolphthalein in feed for 2 years resulted in increased incidences of atypical hyperplasia of the thymus in males and females, degeneration of the germinal epithelium of the testis in males, and ovarian hyperplasia in females. Exposure of mice to phenolphthalein in feed for 2 years resulted in decreased incidences of hepatocellular neoplasms and nonneoplastic lesions in males and females. Synonyms: 3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone; 3,3-bis( p-hydroxyphenyl)phthalide; a-p -hydroxyphenyl)-a- (4-oxo-2,5-cyclohexadien-1-ylidene)- o-toluic acid Trade names: Agoral®, Alophen®, Colax®, Correctol®, Dialose®, Doxidan®, Espotabs®, Evac-U-Gen®, Evac-U-Lax®, Ex-Lax®, Feen-A-Mint®, FemiLax®, Kondremul®, LaxCaps®, Lax-Pills®, Medilax®, Modane®, Phenolax®, Prulet®
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PMID:NTP Toxicology and Carcinogenesis Studies of Phenolphthalein (CAS No. 77-09-8) in F344/N Rats and B6C3F1 Mice (Feed Studies). 1257 99

Sodium xylenesulfonate is used as a hydrotrope, an organic compound that increases the ability of water to dissolve other molecules. Sodium xylenesulfonate is a component in a variety of widely used shampoos and liquid household detergents where it can constitute up to 10% of the total solution. Because of its widespread use, the potential for human exposure to sodium xylenesulfonate is great. Male and female F344/N rats and B6C3F1 mice were administered sodium xylenesulfonate in water or 50% ethanol dermally for 17 days, 14 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, L5178Y mouse lymphoma cells, and cultured Chinese hamster ovary cells. 17-DAY STUDY IN RATS: Groups of five male and five female rats were administered 300 mL of 0, 5, 15, 44, 133, or 400 mg/mL sodium xylenesulfonate in distilled water by dermal application 5 days per week for 17 days. All rats survived to the end of the study. Final mean body weights and body weight gains of dosed rats were similar to those of the control groups. Dermal applications of 300 mL of 5, 15, 44, 133, and 400 mg/mL delivered average daily doses of approximately 10, 30, 90, 260, and 800 mg sodium xylenesulfonate/kg body weight to males and 13, 40, 120, 330, and 1,030 mg/kg to females. Clinical findings generally involved the skin of dosed animals and included tan or brown skin discoloration and crusty white deposits (presumed to be dried chemical) at the site of application. Neither of these observations were considered significant findings. The relative liver weights of 133 and 400 mg/mL male and female rats were significantly greater than those of the control groups, but the absolute liver weights were not increased and the biological significance of the relative differences in liver weight was unclear. In males and females, the few lesions observed grossly and microscopically were generally attributed to repeated clipping and were not considered related to chemical administration. 17-DAY STUDY IN MICE: Groups of five male and five female mice were administered 100 mL of 0, 5, 15, 44, 133, or 400 mg/mL sodium xylenesulfonate in distilled water by dermal application 5 days per week for 17 days. All mice survived to the end of the study. Final mean body weights and body weight gains of dosed mice were similar to those of the controls. Dermal applications of 5, 15, 44, 133, and 400 mg/mL delivered average daily doses of approximately, 20, 60, 190, 540, and 1,600 mg sodium xylenesulfonate/kg body weight to males and 26, 80, 220, 680, and 2,000 mg/kg to females. Clinical findings included crusty white deposits (presumed to be dried chemical) at the site of application in two 133 mg/mL males and in all 400 mg/mL males and females. The absolute and relative liver weights of 15 and 44 mg/mL males and 400 mg/mL males and females were significantly greater than those of the control groups, but the biological significance of these differences was unclear. The few skin lesions observed grossly and microscopically in males and females were generally attributed to repeated clipping and were not considered related to chemical administration. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were administered 300 mL of 0, 5, 15, 44, 133, or 400 mg/mL sodium xylenesulfonate in 50% ethanol by dermal application for 14 weeks. For special hematology and clinical pathology studies, additional groups of 10 male and 10 female rats were administered 0, 5, 15, 44, 133, or 400 mg/mL sodium xylenesulfonate in 50% ethanol by dermal application for 14 weeks. All rats survived to the end of the study. Final mean body weights and body weight gains of dosed male and female rats were similar to those of the control groups. Dermal applications of 5, 15, 44, 133, and 400 mg/mL delivered average daily doses of approximately 6, 20, 60, 170, and 500 mg sodium xylenesulfonate/kg body weight to males and 10, 30, 90, 260, and 800 mg/kg to females. The only notable clinical finding was brown discoloration of the skin at the site of application in dosed animals. Hemaation in dosed animals. Hematology and clinical chemistry parameters of dosed groups of males and females were significantly different from those of the controls in several instances, but these differences were sporadic and did not demonstrate a treatment relationship. The absolute and relative liver weights of males receiving 44, 133, or 400 mg/mL were significantly less than those of the control group, but the biological significance of these differences was unclear, and there were no treatment-related histopathologic effects in the liver. There were no significant differences in liver weights in female rats. Minimal hyperplasia of the epidermis at the site of application occurred in both male and female rats in the control group as well as most dosed groups. The incidence of epidermal hyperplasia in 400 mg/mL males was possibly chemical related. 14-Week Study in Mice: Groups of 10 male and 10 female mice were administered 100 mL of 0, 5, 15, 44, 133, or 400 mg/mL sodium xylenesulfonate in 50% ethanol by dermal application for 14 weeks. There were no chemical-related deaths. The mean body weight gain of the 400 mg/mL males was significantly greater than that of the control group. Dermal applications of 5, 15, 44, 133, and 400 mg/mL delivered average daily doses of approximately 17, 40, 140, 440, and 1,300 mg sodium xylenesulfonate/kg body weight to males and 20, 60, 170, 530, and 1,630 mg/kg to females. There were no clinical findings related to sodium xylenesulfonate administration. Epidermal hyperplasia occurred in one 44 mg/mL female, two 133 mg/mL males, five 400 mg/mL males, and four 400 mg/kg females. Hyperplasia of the epidermis in 400 mg/mL males and females was probably related to chemical administration. Chronic inflammation of the skin occurred primarily in the control groups of males and females. These lesions consisted of mononuclear inflammatory cells in the dermis. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were dermally administered 0, 60, 120, or 240 mg sodium xylenesulfonate/kg body weight in 50% ethanol for 104 weeks. Survival, Body Weights, and Clinical Findings: Survival of dosed males and females was similar to that of the control groups. Mean body weights of dosed males and females were similar to those of the controls throughout the study. In male groups, there were no clinical findings considered treatment related. In females, clinical findings were limited to irritation at the site of application in one control female, four 120 mg/kg females, and two 240 mg/kg females. Pathology Findings: There were no neoplasms at any site (including the skin) that were considered treatment related.Low incidences of hyperplasia of the epidermis at the site of application occurred in males in the 60, 120, and 240 mg/kg groups. Low incidences of hyperplasia of the epidermis at the site of application also occurred in females in the 120 and 240 mg/kg groups, and they occurred with a significant positive trend. Low incidences of hyperplasia of the sebaceous gland occurred in control and 60 mg/kg males and in control, 120 mg/kg, and 240 mg/kg females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were dermally administered 0, 182, 364, or 727 mg sodium xylenesulfonate/kg body weight in 50% ethanol for 104 to 105 weeks. Survival, Body Weights, and Clinical Findings: Survival of dosed males and females was similar to that of the control groups. Mean body weights of dosed males and females were generally similar to those of the controls throughout the study; however, the mean body weights of 727 mg/kg females were greater than those of the control group from week 85 to week 97. With the exception of irritation at the site of application in one 364 mg/kg female, there were no clinical findings related to sodium xylenesulfonate administration. Pathology Findings: There were no neoplasms at any site (including the skin) that were considered treatment related.Hyperplasia of the epidermis occurred in control,364 mg/kg, and 727 mg/kg males and in control and dosed females. In male mice, the incidences occurred with a significant positive trend. Focal ulceration occurred in one 727 mg/kg male and in one female in each dose group. In males and females from control and dosed groups, the incidences of hepatocellular adenoma, hepatocellular carcinoma, and hepato- cellular adenoma or carcinoma (combined) were generally higher than those expected by spontaneous occurrence. The incidences of hepatocellular neoplasms in some groups of males and females exceeded the NTP historical control range. Male mice had a pattern of nonneoplastic liver lesions along with silver stained positive helical organisms within the liver which suggests an infection with Helicobacter hepaticus. The findings in this study of sodium xylenesulfonate were not considered to have been significantly impacted by the infection with H. hepaticus or its associated hepatitis. GENETIC TOXICOLOGY: Sodium xylenesulfonate was not mutagenic in Salmonella typhimurium strain TA98, TA100, TA1535, or TA1537 with or without induced liver S9. Equivocal results were obtained in a mutation assay with mouse lymphoma cells in the presence of induced S9; no evidence of mutagenicity was noted without S9 in this assay. In cytogenetic tests with sodium xylenesulfonate in cultured Chinese hamster ovary cells, significant increases in sister chromatid exchanges were observed in the absence of S9 only, and no increases in chromosomal aberrations were observed with or without S9. CONCLUSIONS: Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity of sodium xylenesulfonate in male or female F344/N rats administered 60, 120, or 240 mg/kg or in male or female B6C3F1 mice administered 182, 364, or 727 mg/kg. Increased incidences of epidermal hyperplasia in female rats and male mice may have been related to exposure to sodium xylenesulfonate. Synonyms: Benzenesulfonic acid, dimethyl-, sodium salt; xylenesulfonic acid, sodium salt; sodium dimethylbenzenesulfonate; xylenesulfonic acid, sodium salt Trade names: Conco SXS; Cyclophil; SXS 30; Eletesol SX 30; Naxonate; Naxonate G; Richonate SXS; Stepanate SXS; Stepanate X; SXS 40; Ultrawet 40SX
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PMID:NTP Toxicology and Carcinogenesis Studies of Technical Grade Sodium Xylenesulfonate (CAS No. 1300-72-7) in F344/N Rats and B6C3F1 Mice (Dermal Studies). 1257

Cobalt sulfate is used in the electroplating and electro chemical industries. It is also used as a coloring agent for ceramics and as a drying agent in inks, paints, varnishes, and linoleum. Cobalt sulfate may be added to animal feed as a mineral supplement and has been used as a top dressing on pasture lands. Cobalt sulfate was nominated by the National Cancer Institute for study based on a lack of information on the toxicity of soluble salts. Male and female F344/N rats and B6C3F1 mice were exposed to cobalt sulfate heptahydrate (approximately 99% pure) by inhalation for 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium. The results of prechronic inhalation toxicity studies were reported previously (Bucher et al., 1990; NTP, 1991). 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to aerosols containing 0, 0.3, 1.0, or 3.0 mg/m3 cobalt sulfate heptahydrate 6 hours per day, 5 days per week, for 105 weeks. Survival and Body Weights Survival of exposed males and females was similar to that of the chamber controls. Mean body weights of exposed male and female rats were similar to those of the chamber controls throughout the study. Pathology Findings The incidences and severities of proteinosis, alveolar epithelial metaplasia, granulomatous alveolar inflammation, and interstitial fibrosis were markedly greater in all exposed groups of male and female rats than in the chamber controls. The incidences of alveolar epithelial hyperplasia in all groups of exposed males and in females exposed to 3.0 mg/m3 were significantly greater than those in the chamber control groups, as were the incidences of squamous metaplasia in 1.0 mg/m3 females and atypical alveolar epithelial hyperplasia in 3.0 mg/m3 females. In 3.0 mg/m3 males, the combined incidence of alveolar/ bronchiolar neoplasms (adenoma and/or carcinoma) was significantly greater than in the chamber controls. In female rats exposed to 1.0 or 3.0 mg/m3, the incidences of alveolar/bronchiolar neoplasms were significantly greater than those in the chamber control group and exceeded the NTP historical control ranges. A squamous cell carcinoma was observed in one 1.0 mg/m3 and one 3.0 mg/m3 female. The incidences of benign, complex, or malignant pheochromocytoma (combined) in 1.0 mg/m3 males and in 3.0 mg/m3 females were significantly greater than those in the chamber controls and exceeded the historical control ranges. Hyperplasia of the lateral wall of the nose, atrophy of the olfactory epithelium, and squamous metaplasia of the epiglottis were observed in all exposed groups of males and females, and the severities of these lesions increased with increasing exposure concentration. The incidences of squamous metaplasia of the lateral wall of the nose and metaplasia of the olfactory epithelium were increased in 3.0 mg/m3 males and females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to aerosols containing 0, 0.3, 1.0, or 3.0 mg/m3 cobalt sulfate heptahydrate 6 hours per day, 5 days per week, for 105 weeks. Survival and Body Weights Survival of exposed males and females was similar to that of the chamber controls. Mean body weights of 3.0 mg/m3 male mice were less than those of the chamber controls from week 96 until the end of the study. The mean body weights of all exposed groups of female mice were generally greater than those of the chamber controls from week 20 until the end of the study. Pathology Findings The incidences of diffuse histiocytic cell infiltration in 3.0 mg/m3 males and of focal histiocytic cell infil tration in 3.0 mg/m3 females were significantly greater than those in the chamber controls. The incidences of alveolar/bronchiolar neoplasms in 3.0 mg/m3 males and females were significantly greater than those in the chamber control groups. The combined incidences of alveolar/bronchiolar adenoma or carcinoma and the incidences of alveolar/bronchiolar carcinoma in 3.0 mg/m3 males and females and the incidence of alveolar/bronchiolar adenoma in 3.0 mg/m3 females exceeded the NTP historical crical control ranges for inhalation studies. The incidences of atrophy of the olfactory epithelium in 1.0 and 3.0 mg/m3 males and females and hyper plasia of the olfactory epithelium in 3.0 mg/m3 males and females were significantly greater than in the chamber controls. Squamous metaplasia of the larynx was observed in all exposed groups of males and females. Male mice had a pattern of nonneoplastic liver lesions along with silver-staining helical organisms within the liver, characteristic of an infection with Helico bacter hepaticus. In NTP studies with H. hepaticus- associated hepatitis, increased incidences of hemangiosarcoma were seen in the liver of male mice. In this study of cobalt sulfate heptahydrate, incidences of hemangiosarcoma were increased in exposed groups of male mice. Because of the above association, interpretation of the increased incidences of hemangiosarcoma in the livers of male mice was confounded. Incidences of lesions at other sites in this study of cobalt sulfate heptahydrate were not considered to have been significantly impacted by the infection with H. hepaticus or its associated hepatitis. GENETIC TOXICOLOGY: Cobalt sulfate heptahydrate was mutagenic in S. typhimurium strain TA100 with and without liver S9 metabolic activation enzymes; no mutagenic activity was detected in strain TA98 or TA1535, with or without S9. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of cobalt sulfate heptahydrate in male F344/N rats based on increased incidences of alveolar/bronchiolar neoplasms. Marginal increases in incidences of pheochromocytomas of the adrenal medulla may have been related to exposure to cobalt sulfate heptahydrate. There was clear evidence of carcinogenic activity in female F344/N rats based on increased incidences of alveolar/bronchiolar neo-plasms and pheochromocytomas of the adrenal medulla in groups exposed to cobalt sulfate heptahydrate. There was clear evidence of carcinogenic activity of cobalt sulfate heptahydrate in male and female B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. Exposure to cobalt sulfate heptahydrate caused a spectrum of inflammatory, fibrotic, and proliferative lesions in the respiratory tract of male and female rats and mice. Synonyms: Bieberite; cobalt(II) sulfate (1:1) heptahydrate; cobalt monosulfate heptahydrate; cobalt(II) sulphate heptahydrate; sulfuric acid, cobalt(2+) salt (1:1) heptahydrate
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PMID:NTP Toxicology and Carcinogenesis Studies of Cobalt Sulfate Heptahydrate (CAS No. 10026-24-1) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). 1257 2

Pyridine is used as a denaturant in alcohol and anti freeze mixtures, as a solvent for paint, rubber, and polycarbonate resins, and as an intermediate in the manufacture of insecticides, herbicides, and fungicides. It is used in the production of piperidine, an intermediate in the manufacture of rubber and mepiquat chloride, and as an intermediate and solvent in the preparation of vitamins and drugs, dyes, textile water repellants, and flavoring agents in food. Pyridine was nominated for study because of its large production volume and its use in a variety of food, medical, and industrial products. Male and female F344/N rats, male Wistar rats, and male and female B6C3F1 mice were exposed to pyridine (approximately 99% pure) in drinking water for 13 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, L5178Y mouse lymphoma cells, cultured Chinese hamster ovary cells, Drosophila melanogaster, and mouse bone marrow cells. 13-WEEK STUDY IN F344/N RATS: Groups of 10 male and 10 female F344/N rats were exposed to pyridine in drinking water at concentrations of 0, 50, 100, 250, 500, or 1,000 ppm (equivalent to average daily doses of 5, 10, 25, 55, or 90 mg pyridine/kg body weight). Two females exposed to 1,000 ppm died during week 1. Final mean body weights of 1,000 ppm males and females and 500 ppm females were significantly less than controls. Water consumption by female rats exposed to 1,000 ppm was less than that by controls. At study termination, evidence of anemia persisted in the 500 and 1,000 ppm males and all exposed groups of females. There was evidence of hepatocellular injury and/or altered hepatic function demonstrated by increased serum alanine aminotransferase and sorbitol dehydrogenase activities and bile acid concentrations in 500 and 1,000 ppm rats. The estrous cycle length of 1,000 ppm females was significantly longer than that of the controls. Liver weights of males and females exposed to 250 ppm or greater were significantly greater than controls. In the liver, the incidences of centrilobular degeneration, hypertrophy, chronic inflammation, and pigmentation were generally increased in 500 and 1,000 ppm males and females relative to controls. In the kidney, the incidences of granular casts and hyaline degeneration (hyaline droplets) were significantly increased in 1,000 ppm males and slightly increased in 500 ppm males; these lesions are consistent with 2u-globulin nephropathy. Additionally, there were increased incidences and/or severities of protein casts, chronic inflammation, mineralization, and regeneration primarily in 500 and 1,000 ppm males. 13-WEEK STUDY IN MALE WISTAR RATS: Groups of 10 male Wistar rats were exposed to pyridine in drinking water at concentrations of 0, 50, 100, 250, 500, or 1,000 ppm (equivalent to average daily doses of 5, 10, 30, 60, or 100 mg/kg). One male rat exposed to 500 ppm died during week 1. Final mean body weights of rats exposed to 250, 500, or 1,000 ppm were significantly less than those of the controls. Water consumption by rats exposed to 1,000 ppm was lower than that by controls. There was evidence of hepatocellular injury and/or altered hepatic function in the 500 and 1,000 ppm groups, similar to that observed in the 13-week study in F344/N rats. Incidences of centrilobular degeneration, hypertrophy, chronic inflammation, and pigmentation in the liver of rats exposed to 500 or 1,000 ppm were significantly increased relative to controls. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to pyridine in drinking water at concentrations of 0, 50, 100, 250, 500, or 1,000 ppm (equivalent to average daily doses of 10, 20, 50, 85, or 160 mg/kg for males and 10, 20, 60, 100, or 190 mg/kg for females). One female mouse exposed to 250 ppm died during week 2. Final mean body weights of female mice exposed to 1,000 ppm were significantly less than those of controls. Water consumption by exposed female mice was lower than that by controls at week 1 but generally slightly higher than controls at week 13. Sperm motirm motility in exposed male mice was significantly decreased relative to controls. Liver weights were significantly increased relative to controls in males exposed to 100 ppm or greater and in 250 and 500 ppm females. No chemical-related lesions were observed in male or female mice. 2-YEAR STUDY IN F344/N RATS: Groups of 50 male and 50 female F344/N rats were exposed to pyridine in drinking water at concentrations of 0, 100, 200, or 400 ppm (equivalent to average daily doses of 7, 14, or 33 mg/kg) for 104 (males) or 105 (females) weeks. Survival, Body Weights, and Water Consumption Survival of exposed males and females was similar to that of controls. Mean body weights of 400 ppm males and females were generally less than those of the controls throughout the study, and those of 200 ppm males and females were less during the second year of the study. Water consumption by males and females exposed to 200 or 400 ppm was generally greater than that by controls. Pathology Findings Incidences of renal tubule adenoma and renal tubule adenoma or carcinoma (combined) in male rats exposed to 400 ppm were significantly increased compared to controls and exceeded the historical control ranges. The findings from an extended evaluation (step section) of the kidneys did not reveal additional carcinomas, but additional adenomas were observed in each group of males. In the standard evaluation, an increased incidence of renal tubule hyperplasia was observed in 400 ppm males compared to controls. Incidences of mononuclear cell leukemia in female rats were significantly increased in the 200 and 400 ppm groups, and the incidence in the 400 ppm group exceeded the historical control range. Exposure concentration-related nonneoplastic liver lesions were observed in males and females, and the incidences were generally increased in groups exposed to 400 ppm. These included centrilobular cytomegaly, cytoplasmic vacuolization, periportal fibrosis, fibrosis, centrilobular degeneration and necrosis, and pigmentation. Bile duct hyperplasia occurred more often in exposed females than in controls. 2-YEAR STUDY IN MALE WISTAR RATS: Groups of 50 male Wistar rats were exposed to pyridine in drinking water at concentrations of 0, 100, 200, or 400 ppm (equivalent to average daily doses of 8, 17, or 36 mg/kg) for 104 weeks. Survival, Body Weights, and Water Consumption Survival of rats exposed to 200 or 400 ppm was significantly less than that of the controls. Mean body weights of rats exposed to 100, 200, or 400 ppm were significantly less than controls. Water consumption was similar by control and exposed rats. Pathology Findings The incidence of testicular interstitial cell adenoma in rats exposed to 400 ppm was significantly increased compared to controls. Incidences of interstitial cell hyperplasia were observed in control and exposed groups and were slightly, but not significantly, increased in rats exposed to 200 or 400 ppm. Severity of nephropathy was marked in all groups, and additional evidence of kidney disease, including mineralization in the glandular stomach, parathyroid gland hyperplasia, and fibrous osteodystrophy, was observed in 100 and 200 ppm rats. The incidences of hepatic centrilobular degeneration and necrosis, fibrosis, periportal fibrosis, and/or pigmentation were increased in one or more exposed groups. 2-YEAR STUDY IN MICE: Groups of 50 male B6C3F1 mice were exposed to pyridine in drinking water at concentrations of 0, 250, 500, or 1,000 ppm (equivalent to average daily doses of 35, 65, or 110 mg/kg) for 104 weeks, and groups of 50 female B6C3F1 mice were exposed to pyridine in drinking water at concentrations of 0, 125, 250, or 500 ppm (equivalent to average daily doses of 15, 35, or 70 mg/kg) for 105 weeks. Survival, Body Weights, and Water Consumption Survival of exposed males and females was similar to that of the controls. Mean body weights of 250 and 500 ppm females were less than controls. Water consumption by males exposed to 250 or 500 ppm was generally greater than that by controls during the last year of the study; male mice exposed to 1,000 ppm consumed less water than controls throughout the study. Water consumption by exposed females was generally lower than that by controls during the first year of the study, but greater than controls during the second year. Pathology Findings Hepatocellular neoplasms, including hepatoblastomas, in exposed male and female mice were clearly related to pyridine exposure. Additionally, many mice had multiple hepatocellular neoplasms. The incidences of hepatocellular neoplasms in exposed males and females generally exceeded the historical control ranges for drinking water studies. Neoplasms from control mice, 1,000 ppm males, and 500 ppm females were negative when stained for p53 protein. GENETIC TOXICOLOGY: Pyridine was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 or in L5178Y mouse lymphoma cells, with or without S9 metabolic activation, and it did not induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells, with or without S9. Pyridine was tested for induction of sex-linked recessive lethal mutations in adult male Drosophila melanogaster, and mixed results were obtained. In one experiment, administration by injection gave negative results, but feeding produced an equivocal response. A second experiment generated negative results by injection and feeding. A third experiment showed significant increases in sex-linked recessive lethal mutations in flies treated with pyridine by injection but not by feeding. Overall, results of the sex-linked recessive lethal mutations test in Drosophila melanogaster were considered negative by feeding and equivocal by injection. Results of a single reciprocal translocation test in male Drosophila melanogaster were negative. No induction of chromosomal aberrations or micronuclei was noted in bone marrow cells of male mice administered pyridine via intraperitoneal injection. CONCLUSIONS: Under the conditions of these 2-year drinking water studies, there was some evidence of carcinogenic activity of pyridine in male F344/N rats based on increased incidences of renal tubule neoplasms. There was equivocal evidence of carcinogenic activity of pyridine in female F344/N rats based on increased incidences of mononuclear cell leukemia. There was equivocal evidence of carcinogenic activity in male Wistar rats based on an increased incidence of interstitial cell adenoma of the testis. There was clear evidence of carcinogenic activity of pyridine in male and female B6C3F1 mice based on increased incidences of malignant hepatocellular neoplasms. In F344/N rats, exposure to pyridine resulted in increased incidences of centrilobular cytomegaly and degeneration, cytoplasmic vacuolization, and pigmentation in the liver of males and females; periportal fibrosis, fibrosis, and centrilobular necrosis in the liver of males; and bile duct hyperplasia in females. In male Wistar rats, pyridine exposure resulted in increased incidences of centrilobular degeneration and necrosis, fibrosis, periportal fibrosis, and pigmentation in the liver, and, secondary to kidney disease, mineralization in the glandular stomach and parathyroid gland hyperplasia. Synonyms: Azabenzene, azine
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PMID:NTP Toxicology and Carcinogenesis Studies of Pyridine (CAS No. 110-86-1) in F344/N Rats, Wistar Rats, and B6C3F1 Mice (Drinking Water Studies). 1257 3

Ethylbenzene is mainly used in the manufacture of styrene. Ethylbenzene is also a major component of mixed xylenes used as solvents in agricultural and home insecticide sprays, rubber and chemical manufacturing, and household degreasers, paints, adhesives, and rust preventives. Ethylbenzene is also used as an antiknock agent in aviation and motor fuels. Ethylbenzene was nominated for study by the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) because of its potential for widespread human exposure and because of its structural similarity to benzene and toluene. Male and female F344/N rats and B6C3F1 mice were exposed to ethylbenzene (greater than 99% pure) by inhalation for 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, mouse lymphoma cells, cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes. In previously reported 13-week toxicity studies in which F344/N rats and B6C3F1 mice were exposed to ethylbenzene by whole body inhalation exposure, no histopathologic changes were observed (NTP, 1992). 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were exposed to 0, 75, 250, or 750 ppm ethylbenzene by inhalation, 6 hours per day, 5 days per week, for 104 weeks. Survival, Body Weights, and Clinical Findings Survival of male rats in the 750 ppm group was significantly less than that of the chamber controls. Mean body weights of 250 and 750 ppm males were generally less than those of the chamber controls beginning at week 20. Mean body weights of exposed groups of females were generally less than those of chamber controls during the second year of the study. Pathology Findings In male rats exposed to 750 ppm, the incidences of renal tubule adenoma and adenoma or carcinoma (combined) were significantly greater than the chamber control incidences. In addition, the incidence of renal tubule hyperplasia in 750 ppm males was significantly greater than that in the chamber controls. The findings from an extended evaluation (step section) of the kidneys showed a significant increase in the incidences of renal tubule adenoma and hyperplasia in 750 ppm males and females; the incidence of renal tubule adenoma or carcinoma (combined) was significantly increased in 750 ppm males. The severities of nephropathy in 750 ppm male and all exposed female rats were significantly increased relative to the chamber controls. The incidence of interstitial cell adenoma in the testis of 750 ppm males was significantly greater than that in the chamber control group and slightly exceeded the historical control range for inhalation studies. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were exposed to 0, 75, 250, or 750 ppm ethylbenzene by inhalation, 6 hours per day, 5 days per week, for 103 weeks. Survival, Body Weights, and Clinical Findings Survival of exposed groups of male and female mice was similar to that of the chamber controls. Mean body weights of female mice exposed to 75 ppm were greater than those of the chamber controls from week 72 until the end of the study. Pathology Findings In 750 ppm males, the incidences of alveolar/ bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) were significantly greater than those in the chamber control group but were within the NTP historical control ranges. The incidence of alveolar epithelial metaplasia in 750 ppm males was significantly greater than that in the chamber controls. In 750 ppm females, the incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined) were significantly greater than those in the chamber control group but were within the historical control ranges. The incidence of eosinophilic foci in 750 ppm females was significantly increased compared to that in the chamber controls. There was a spectrum of nonneoplastic liver changes related to ethylbenzene exposure in male mice, including syncytial alteration of hepatocytes, hepatocellular hypertrophy, and hepatocyte necrosis. rosis. The incidences of hyperplasia of the pituitary gland pars distalis in 250 and 750 ppm females and the incidences of thyroid gland follicular cell hyperplasia in 750 ppm males and females were significantly increased compared to those in the chamber control groups. GENETIC TOXICOLOGY: Ethylbenzene gave little indication of mutagenicity, in vitro or in vivo. No induction of mutations was noted in Salmonella typhimurium strain TA97, TA98, TA100, or TA1535 with or without S9 metabolic activation, and no increases in sister chromatid exchanges or chromosomal aberrations were observed in cultured Chinese hamster ovary cells treated with ethylbenzene, with or without S9. In the mouse lymphoma assay, a significant mutagenic response was noted in the absence of S9, but only at the highest nonlethal dose tested and with accompanying cytotoxicity; the test was not performed with S9. No increases in the frequency of micronucleated erythrocytes were observed in vivo in peripheral blood samples from male and female mice exposed to ethylbenzene for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was clear evidence of carcinogenic activity of ethylbenzene in male F344/N rats based on increased incidences of renal tubule neoplasms. The incidences of testicular adenoma were also increased. There was some evidence of carcinogenic activity of ethylbenzene in female F344/N rats based on increased incidences of renal tubule adenomas. There was some evidence of carcinogenic activity of ethylbenzene in male B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. There was some evidence of carcinogenic activity of ethylbenzene in female B6C3F1 mice based on increased incidences of hepatocellular neoplasms. Exposure of male and female rats to ethylbenzene resulted in increased incidences of renal tubule hyperplasia and increased severities of nephropathy. Exposure of male mice to ethylbenzene resulted in increased incidences of alveolar epithelial metaplasia, syncytial alteration of hepatocytes, hepatocellular hypertrophy, hepatocyte necrosis, and thyroid gland follicular cell hyperplasia. In female mice, ethylbenzene exposure resulted in increased incidences of eosinophilic foci of the liver, pituitary gland pars distalis hyperplasia, and thyroid gland follicular cell hyperplasia. Synonyms: EB; ethylbenzol; phenylethane
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PMID:NTP Toxicology and Carcinogenesis Studies of Ethylbenzene (CAS No. 100-41-4) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). 1257 7

Molybdenum is an essential element for the function of nitrogenase in plants and as a cofactor for enzymes including xanthine oxidoreductase, aldehyde oxidase, and sulfide oxidase in animals. Molybdenum trioxide is used primarily as an additive to steel and corrosion-resistant alloys. It is also used as a chemical intermediate for molybdenum products; an industrial catalyst; a pigment; a crop nutrient; components of glass, ceramics, and enamels; a flame retardant for polyester and polyvinyl chloride resins; and a reagent in chemical analyses. Molybdenum trioxide was nominated by the NCI for toxicity and carcinogenicity studies as a representative inorganic molybdenum compound. The production of molybdenum trioxide is the largest of all the molybdenum compounds examined. Male and female F344/N rats and B6C3F1 mice were exposed to molybdenum trioxide (approximately 99% pure) by inhalation for 14 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and cultured Chinese hamster ovary cells. 14-DAY STUDY IN RATS: Groups of five male and five female F344/N rats were exposed to 0, 3, 10, 30, 100, or 300 mg molybdenum trioxide/m(3). Rats were exposed for 6 hours per day, 5 days per week, for a total of 10 exposure days during a 14-day period. All rats survived to the end of the study. The final mean body weights of male rats exposed to 100 mg/m(3) and male and female rats exposed to 300 mg/m(3) were significantly lower than those of the control groups. Male rats exposed to 300 mg/m(3) lost weight during the study. There were no clinical findings related to exposure to molybdenum trioxide. No chemical-related lesions were observed. 14-DAY STUDY IN MICE: Groups of five male and five female B6C3F1 mice were exposed to 0, 3, 10, 30, 100, or 300 mg molybdenum trioxide/m(3). Mice were exposed 6 hours per day, 5 days per week, for a total of 10 exposure days during a 14-day period. All mice survived to the end of the study. Final mean body weights of male and female mice exposed to 300 mg/m(3) were significantly lower than those of the control groups. Male mice exposed to 300 mg/m(3) lost weight during the study. There were no clinical findings related to exposure to molybdenum trioxide. No chemical-related lesions were observed. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were exposed to molybdenum trioxide by inhalation at concentrations of 0, 1, 3, 10, 30, or 100 mg/m(3) for 6.5 hours per day, 5 days per week, for 13 weeks. All rats survived to the end of the study. The final mean body weights of exposed rats were similar to those of the control groups. No clinical findings related to molybdenum trioxide exposure were observed. There were no significant chemical-related differences in absolute or relative organ weights, hematology or clinical chemistry parameters, sperm counts or motility, or liver copper concentrations between control and exposed rats. No chemical-related lesions were observed. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to molybdenum trioxide by inhalation at concentrations of 0, 1, 3, 10, 30, or 100 mg/m(3) for 6.5 hours per day, 5 days per week, for 13 weeks. All mice survived to the end of the study. The final mean body weights of exposed mice were similar to those of the control groups. There were no chemical-related clinical findings. There were no significant differences in absolute or relative organ weights or sperm counts or motility between control and exposed mice. There were significant increases in liver copper concentrations in female mice exposed to 30 mg/m(3) and in male and female mice exposed to 100 mg/m(3) compared to those of the control groups. No chemical-related lesions were observed. 2-YEAR STUDIES IN RATS: Groups of 50 male and 50 female F344/N rats were exposed to molybdenum trioxide by inhalation at concentrations of 0, 10, 30, or 100 mg/m(3). Rats were exposed for 6 hours per day, 5 days per week, for 106 weeks. Survival, Body Weights, and Special Studies: Survival rates of exposed maleed male and female rats were similar to those of the control groups. Mean body weights of exposed groups of male and female rats were similar to those of the control groups throughout the study. There was a significant exposure-dependent increase in blood molybdenum concentration in exposed rats. Blood concentrations of molybdenum in exposed male rats were greater than those in exposed female rats. There were no toxicologically significant differences in bone density or curvature between control and exposed rats. Pathology Findings: The incidences of alveolar/bronchiolar adenoma or carcinoma (combined) were increased in male rats with a marginally significant positive trend. No increase in the incidences of lung neoplasms occurred in female rats. Incidences of chronic alveolar inflammation in male and female rats exposed to 30 or 100 mg/m(3) were significantly greater than those in the control groups. No nasal or laryngeal neoplasms were attributed to exposure to molybdenum trioxide. Incidences of hyaline degeneration in the nasal respiratory epithelium in 30 and 100 mg/m(3) males and in all exposed groups of females were significantly greater than those in the control groups. The incidences of hyaline degeneration in the nasal olfactory epithelium of all exposed groups of females were significantly greater than that in the control group. In the larynx, incidences of squamous metaplasia of the epithelium lining the base of the epiglottis in all exposed groups of male and female rats were significantly greater than those in the control groups and increased with increasing exposure concentration. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were exposed to molybdenum trioxide by inhalation at concentrations of 0, 10, 30, or 100 mg/m(3). Mice were exposed for 6 hours per day, 5 days per week, for 105 weeks. Survival, Body Weights, and Special Studies: The survival rate of male mice exposed to 30 mg/m(3) was marginally lower than that of the control group; survival rates of 10 and 100 mg/m(3) males and of all exposed groups of females were similar to those of the control groups. Mean body weights of exposed male mice were generally similar to those of the control group throughout the study. Mean body weights of exposed female mice were generally greater than those of the control group from week 11 until the end of the study. There was a significant exposure-dependent increase in blood molybdenum concentration in exposed mice. There were no toxicologically significant differences in bone density or curvature between control and exposed mice. Pathology Findings: The incidences of alveolar/bronchiolar carcinoma in all exposed groups of males were significantly greater than that in the control group. Incidences of alveolar/bronchiolar adenoma in females in the 30 and 100 mg/m(3) groups were significantly greater than that in the control group. Incidences of alveolar/bronchiolar adenoma or carcinoma (combined) in 10 and 30 mg/m(3) males and in 100 mg/m(3) females were significantly greater than those in the control groups and exceeded the historical control ranges for 2-year NTP inhalation studies. Incidences of metaplasia of the alveolar epithelium of minimal severity in the centriacinar region of the lung were significantly increased in all exposed groups of mice. The incidences of histiocyte cellular infiltration in all exposed groups of males were significantly greater than that in the control group. Incidences of hyaline degeneration of the respiratory epithelium of the nasal cavity in 100 mg/m(3) males and females and hyaline degeneration of the olfactory epithelium of the nasal cavity in 100 mg/m(3) females were significantly greater than those in the control groups. The incidences of squamous metaplasia of the epithelium lining the base of the epiglottis were significantly increased in all exposed groups of males and females. In both male and female mice, the incidences of hyperplasia of the laryngeal epithelium in level II of the larynx increased with increasing exposure concentration. The increase was statistically significant only in mice exposed to 100 mg/m(3) with 82% of male and 70% of female mice affected. GENETIC TOXICOLOGY: Molybdenum trioxide was not mutagenic in any of five strains of Salmonella typhimurium, and it did not induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells in vitro. All tests were conducted with and without S9 metabolic activation enzymes. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was equivocal evidence of carcinogenic activity of molybdenum trioxide in male F344/N rats based on a marginally significant positive trend of alveolar/bronchiolar adenoma or carcinoma (combined). There was no evidence of carcinogenic activity of molybdenum trioxide in female F344/N rats exposed to 10, 30, or 100 mg/m(3). There was some evidence of carcinogenic activity of molybdenum trioxide in male B6C3F1 mice based on increased incidences of alveolar/bronchiolar carcinoma and adenoma or carcinoma (combined). There was some evidence of carcinogenic activity of molybdenum trioxide in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar adenoma and adenoma or carcinoma (combined). Exposure of male and female rats to molybdenum trioxide by inhalation resulted in increased incidences of chronic alveolar inflammation, hyaline degeneration of the respiratory epithelium, hyaline degeneration of the olfactory epithelium (females), and squamous metaplasia of the epiglottis. Exposure of male and female mice to molybdenum trioxide by inhalation resulted in increased incidences of metaplasia of the alveolar epithelium, histiocyte cellular infiltration (males), hyaline degeneration of the respiratory epithelium, hyaline degeneration of the olfactory epithelium (females), squamous metaplasia of the epiglottis, and hyperplasia of the larynx. Synonyms: Molybdic oxide; molybdic trioxide; molybdic anhydride; molybdenum (VI) oxide; molybdenum peroxide; molybdic acid anhydride; molybdenum anhydride; natural molybdite; molybdena
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PMID:NTP Toxicology and Carcinogenesis Studies of Molybdenum Trioxide (CAS No. 1313-27-5) in F344 Rats and B6C3F1 Mice (Inhalation Studies). 1258 14

Nitromethane is used as a rocket and engine fuel; as a synthesis intermediate for agricultural fumigants, biocides, and other products; as a solvent; and as an explosive in mining, oil-well drilling, and seismic exploration. It has been detected in air, in surface and drinking water, and in cigarette smoke. Nitromethane was studied because of the potential for widespread human exposure and because it is structurally related to the carcinogens 2-nitropropane and tetranitromethane. Male and female F344/N rats and B6C3F1 mice received nitromethane (purity 98% or greater) by inhalation for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and peripheral blood erythrocytes of mice. 16-DAY STUDY IN RATS: Groups of five male and five female rats were exposed to 0, 94, 188, 375, 750, or 1,500 ppm nitromethane by inhalation, 6 hours per day, 5 days per week, for 16 days. All rats survived until the end of the study. The mean body weight gain of male rats in the 1,500 ppm group was slightly but significantly less than that of the controls; the final mean body weights and mean body weight gains of exposed females were similar to those of the controls. Clinical findings in all male and female rats in the 1,500 ppm groups included increased preening, rapid breathing, hyperactivity early in the study, and hypoactivity and loss of coordination in the hindlimbs near the end of the study. The relative liver weights of all exposed groups of male rats and the absolute and relative liver weights of females exposed to 375 ppm or greater were significantly greater than those of the controls. Minimal to mild degeneration of the olfactory epithelium was observed in the nose of males and females exposed to 375 ppm or greater. Sciatic nerve degeneration was present in all male and female rats exposed to 375 ppm or greater; rats exposed to 750 or 1,500 ppm also had reduced myelin around sciatic axons. 16-DAY STUDY IN MICE: Groups of five male and five female mice were exposed to 0, 94, 188, 375, 750, or 1,500 ppm nitromethane by inhalation, 6 hours per day, 5 days per week, for 16 days. All mice survived to the end of the study. The final mean body weights and weight gains of exposed males and females were similar to those of the controls. Clinical findings included hypoactivity and tachypnea in male and female mice in the 1,500 ppm groups. Absolute and relative liver weights of male mice in the 750 and 1,500 ppm groups and female mice in all exposed groups and the relative liver weight of males in the 375 ppm group were significantly greater than those of the controls. Degeneration of the olfactory epithelium of the nose was observed microscopically in all males and females exposed to 375 ppm or greater; this lesion was of minimal severity in males and minimal to mild severity in females. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to 0, 94, 188, 375, 750, or 1,500 ppm nitromethane by inhalation, 6 hours per day, 5 days per week, for 13 weeks. All rats survived to the end of the study. The final mean body weight and weight gain of male rats in the 1,500 ppm group were significantly less than those of the controls. Clinical findings included hindlimb paralysis in rats in the 750 and 1,500 ppm groups. Inhalation exposure of rats to nitromethane resulted in an exposure concentration-dependent, microcytic, responsive anemia; anemia was most pronounced in males and females exposed to 375 ppm or greater. The presence of schistocytes, Heinz bodies, and spherocytes and increased mean cell hemoglobin concentration and methemoglobin concentration were evidence that a hemolytic process was occurring; this hemolytic process could have accounted, in part, for the anemia. Thrombocytosis accompanied the anemia and would be consistent with a reactive bone marrow or could have been due to the erroneous inclusion of small erythrocyte fragments as part of the platelet count. On day 23, transient decreases in serum triiodothyronine, thyroxine, and fr and free thyroxine were observed in male rats exposed to 375 ppm or greater and female rats exposed to 750 or 1,500 ppm. There was little or no pituitary response to the thyroid hormone decreases, as evidenced by the lack of significantly increased concentrations of thyroid-stimulating hormone in exposed rats. No biologically significant differences in organ weights were observed. The forelimb and hindlimb grip strengths of males in the 1,500 ppm group were significantly less than those of the controls. The hindlimb grip strengths of females in the 750 and 1,500 ppm groups were also significantly less than the control value. Minimal to mild hyperplasia of the bone marrow was observed microscopically in male rats in the 750 and 1,500 ppm groups and in females exposed to 188 ppm or greater. Nasal lesions in exposed males and females included olfactory epithelial degeneration in males and females exposed to 375 ppm or greater and in one female exposed to 188 ppm and respiratory epithelial hyaline droplets and goblet cell hyperplasia in males and females in the 750 and 1,500 ppm groups; the severity of nasal lesions in males and females was minimal to mild. Males and females exposed to 375 ppm or greater had minimal to mild degeneration of the sciatic nerve and the lumbar spinal cord. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to 0, 94, 188, 375, 750, or 1,500 ppm nitromethane by inhalation, 6 hours per day, 5 days per week, for 13 weeks. All mice survived to the end of the study. The final mean body weights and weight gains of exposed mice were generally similar to those of the controls. There were no treatment-related clinical findings. The absolute right kidney weights of all groups of exposed male mice except the 1,500 ppm group and of females exposed to 188 ppm or greater and the relative right kidney weights of all groups of exposed males and of females in the 750 and 1,500 ppm groups were significantly greater than those of the controls. The absolute liver weight of male mice in the 750 ppm group and the relative liver weights of males exposed to 375 ppm or greater were significantly greater than those of the controls. Olfactory epithelial degeneration and respiratory epithelial hyaline droplets were observed microscopically in all male and female mice exposed to 375 ppm or greater. Degeneration also occurred in females in the 188 ppm group, and hyaline droplets occurred in females in the 94 and 188 ppm groups. The average severity of the nasal lesions ranged from minimal to mild in males. In females, the average severity of olfactory epithelial degeneration ranged from minimal to mild and the severity of respiratory epithelial hyaline droplets ranged from minimal to moderate. All males and nine females in the 1,500 ppm groups also had minimal extramedullary hematopoiesis of the spleen. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to 0, 94, 188, or 375 ppm nitromethane by inhalation, 6 hours per day, 5 days per week, for 103 weeks. Survival,Body Weights, and Clinical Findings: There were no significant differences in survival rates between exposed and control male or female rats. The mean body weight of females in the 375 ppm group was slightly greater than that of the control group; the mean body weights of exposed males were generally similar to the mean body weight of the controls throughout the study. Clinical findings were consistent with incidences of mammary gland neoplasms in females exposed to 188 or 375 ppm; no hindlimb paralysis, as occurred in rats in the 13-week study, was observed in male or female rats in the 2-year study. Pathology Findings: The incidences of mammary gland fibroadenoma and fibroadenoma, adenoma, or carcinoma (combined) in female rats in the 188 and 375 ppm groups were significantly greater than those in the controls. Additionally, the incidences of mammary gland carcinoma in the 375 ppm group were significantly greater than those in the controls. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to 0, 188, 375, or 750 ppm nitromethane by inhalation, 6 hours per day, 5 days per week, for 103 weeks. Survival,Body Weights, and ClinicalFindings The survival rate of females in the 750 ppm group was marginally greater than that of the controls. The mean body weights of exposed females were generally slightly greater than the mean body weights of the controls during the study but were generally similar to the mean body weight of the controls at the end of the study. The mean body weights of exposed males were similar to those of the controls throughout the study. Clinical findings included swelling around the eyes and exophthalmos in exposed males and females; these findings were coincident with harderian gland neoplasms. Pathology Findings: The incidences of harderian gland adenoma and adenoma or carcinoma (combined) in exposed mice increased with increasing exposure concentration and were significantly greater in males and females in the 375 and 750 ppm groups than those in the controls. The incidences of harderian gland carcinoma in males and females in the 375 and 750 ppm groups were also slightly greater than those in the controls. Female mice in the 188 and 750 ppm groups had significantly greater incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined) than the controls. The incidences of liver eosinophilic focus increased with increasing exposure concentration, and the incidences in the 375 and 750 ppm groups were significantly greater than the control incidence. The incidences of alveolar/bronchiolar carcinoma in male mice in the 750 ppm group and female mice in the 375 ppm group were significantly greater than those in the controls. Females in the 750 ppm group also had a significantly greater incidence of alveolar/bronchiolar adenoma or carcinoma (combined) and a slightly greater incidence of alveolar/bronchiolar adenoma than the controls. Females in the 375 ppm group had a significantly greater incidence of cellular infiltration of histiocytes in the lung than the controls. The incidences of degeneration and metaplasia of the olfactory epithelium and hyaline degeneration of the respiratory epithelium were significantly greater in exposed male and female mice than those in the controls. Additionally, males in the 375 and 750 ppm groups had significantly greater incidences of inflammation of the nasolacrimal duct than did the controls. GENETIC TOXICOLOGY: Nitromethane was not mutagenic in any tests performed by the NTP. It did not induce mutations in Salmonella typhimurium, with or without S9 metabolic activation, and no induction of sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells exposed to nitromethane was noted with or without S9. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood samples of male and female mice at the end of the 13-week inhalation study of nitromethane. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was no evidence of carcinogenic activity of nitromethane in male F344/N rats exposed to 94, 188, or 375 ppm. There was clear evidence of carcinogenic activity of nitromethane in female F344/N rats based on increased incidences of mammary gland fibroadenomas and carcinomas. There was clear evidence of carcinogenic activity of nitromethane in male B6C3F1 mice based on increased incidences of harderian gland adenomas and carcinomas. There was clear evidence of carcin ogenic activity in female B6C3F1 mice, based on increased incidences of liver neoplasms (primarily adenomas) and harderian gland adenomas and carcinomas. Increased incidences of alveolar/bronchiolar adenomas and carcinomas in male and female mice exposed to nitromethane were also considered to be related to chemical administration. Exposure to nitromethane by inhalation for 2 years resulted in increased incidences of nasal lesions including degeneration and metaplasia of the olfactory epithelium and degeneration of the respiratory epithelium in male and female mice. Synonym: Nitrocarbol
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PMID:NTP Toxicology and Carcinogenesis Studies of Nitromethane (CAS No. 75-52-5) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). 1258 15

t -Butylhydroquinone is used as an antioxidant in cosmetic products such as lipsticks, eye shadows, perfumes, blushers, and skin care preparations at concentrations ranging from 0.1% to 1.0%; the chemical is also used at concentrations up to 0.02% in oils, fats, and meat products to prevent rancidity, and as a polymerization inhibitor for various polyunsaturated polyesters (CIR, 1986). t-Butylhydroquinone was nominated for toxicity and carcinogenicity testing by the Food and Drug Administration. Toxicology and carcinogenicity studies were conducted in F344/N rats and B6C3F(1) mice. Mice were exposed to t-butyl hydroquinone (99% pure) in feed for 13 weeks or 2 years. For rats, exposure to t-butylhydroquinone began in utero and continued through lactation. After weaning, pups were fed diets containing the same levels of t-butylhydroquinone as those given to their respective dams for 13 weeks or for up to 30 months. The oral route of administration was selected for these studies because t-butylhydroquinone is used as a food additive and human exposure occurs predominantly through this route. In addition to the oral route of exposure, rats were exposed prenatally because perinatal exposure to butylated hydroxytoluene (a structurally related chemical) induced hepatocellular neoplasms in rats. Genetic toxicology studies were conducted in Salmonella typhimurium and cultured Chinese hamster ovary cells in vitro and in mouse bone marrow cells in vivo. 13-WEEK STUDY IN RATS: In the perinatal exposure phase of the 13-week study, groups of 10 female rats (F(0)) were fed 0, 2,500, 5,000, 10,000, 20,000, or 40,000 ppm t-butylhydroquinone from 2 weeks prior to cohabitation until the F(1) pups were weaned. F(0) females exposed to 20,000 or 40,000 ppm did not litter. The number of pup deaths in the 5,000 and 10,000 ppm groups was greater than that in the control group, and the average number of surviving pups per litter in the 10,000 ppm group was less than that in the control group. Mean body weights of pups exposed perinatally to 5,000 or 10,000 ppm were lower than that of the controls at the time of weaning. Groups of 10 male and 10 female F(1) rats continued to receive diets containing 0, 2,500, 5,000, or 10,000 ppm t-butylhydroquinone for 13 weeks fol lowing weaning. These dietary levels corresponded to approximately 200, 400, or 800 mg t-butylhydro quinone/kg body weight (males) or 200, 400, or 750 mg/kg (females) per day. All rats survived to the end of the study. The final mean body weights of males and females in the 5,000 and 10,000 ppm groups were significantly lower than those of the controls, as was the mean body weight gain of males exposed to 10,000 ppm. However, interpretation of these findings was complicated by the significantly lower initial mean body weights of the 10,000 ppm groups. Differences in initial body weights were due to in utero exposure to t-butylhydroquinone. Feed consumption by exposed groups of rats was lower than that by controls at week 2, and feed consumption by 5,000 and 10,000 ppm males and 10,000 ppm females was slightly lower than that by controls at the end of the study. Hair discoloration in all exposed groups of rats, except females exposed to 2,500 ppm, was the only clinical observation considered related to chemical exposure. The mean spermatid count, spermatid heads per testis, and spermatid heads per gram of testis were significantly decreased in males exposed to 5,000 ppm. The estrous cycles of females exposed to 2,500 or 5,000 ppm were significantly longer than that of the controls. There were no biologically significant changes in clinical pathology parameters or in organ weights. Increased incidences of hyperplasia of the nasal respiratory epithelium were observed in males exposed to 5,000 ppm and males and females exposed to 10,000 ppm, and an increased incidence of nasal exudate was observed in males in the 10,000 ppm group. Increased incidences of pigmentation were observed in the spleen of male and female rats exposed to 5,000 or 10,000 ppm. Based on lower final mean body weights wer final mean body weights and decreased feed consumption in males and females exposed to 10,000 ppm t-butylhydroquinone, exposure concentrations selected for the long-term rat study were 1,250, 2,500, and 5,000 ppm. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were fed diets containing 0, 2,500, 5,000, 10,000, 20,000, or 40,000 ppm t-butylhydroquinone for 13 weeks. These dietary levels corresponded to approximately 440, 880, 1,950, 4,000, and 8,400 mg t-butylhydro quinone/kg body weight (males) or 500, 1,100, 2,200, 4,600, and 9,000 mg/kg body weight (females) per day. There were no exposure-related deaths. Final mean body weights and body weight gains of males and females exposed to 10,000, 20,000, or 40,000 ppm were significantly less than those of the controls. Feed consumption by exposed mice appeared to be similar to that by controls, but there was excessive scatter of feed by mice exposed to 10,000, 20,000, or 40,000 ppm. Therefore, feed consumption by male and female mice in these groups was likely less than that by controls. Significant increases in segmented neutrophil counts occurred at week 3 and at the end of the study in females exposed to 10,000 ppm and males and females exposed to 20,000 or 40,000 ppm. Left caudal, left epididymis, and left testis weights of males exposed to 10,000 or 40,000 ppm were generally significantly lower than those of the controls. The estrous cycle of females exposed to 40,000 ppm was significantly longer than that of the control group. There were no biologically significant differences in organ weights. Increased incidences and severities of mucosal hyperplasia were observed in the forestomach of males exposed to 20,000 or 40,000 ppm and in females exposed to 10,000, 20,000, or 40,000 ppm, and increased incidences of inflammation were observed in the nose and skin of males and females exposed to 10,000, 20,000, or 40,000 ppm. Increased incidences of hyperplasia also occurred in the skin of males and females exposed to 10,000, 20,000, or 40,000 ppm. Based on lower final mean body weights, increased incidences of inflammation of the nose and skin, increased incidences of forestomach mucosal hyperplasia, and increased severity of nonneoplastic lesions observed in mice exposed to 10,000, 20,000, or 40,000 ppm, exposure concentrations selected for the 2-year study were 1,250, 2,500, and 5,000 ppm. LONG-TERM STUDY IN RATS: In the perinatal exposure phase of the long-term study, groups of 60 female F(0) rats were fed diets containing 0, 1,250, 2,500, or 5,000 ppm t-butyl hydroquinone, beginning 2 weeks prior to cohabitation and continuing until F(1) pups were weaned. Following weaning, groups of 70 male and 70 female F(1) rats continued to receive diets containing 0, 1,250, or 5,000 ppm, and groups of 68 male and 68 female rats continued to receive diets containing 2,500 ppm. The duration of dosing in feed was 123 weeks post-weaning for males and 129 weeks for females. These exposure concentrations resulted in daily doses of approximately 50, 100, and 200 mg t-butylhydro quinone/kg body weight (males) or 60, 120, and 240 mg/kg (females). Ten male and ten female F(1) rats from each exposure group were evaluated at 3 months. Survival, Body Weights, Feed Consumption, and Clinical Findings: Survival of females exposed to 5,000 ppm was significantly greater than that of the control group. The mean body weights of males and females exposed to 5,000 ppm were generally less than those of the controls throughout the study. Feed consumption by exposed groups was similar to that by controls. Clinical findings of hair discoloration in exposed groups of males and females were considered to be related to chemical exposure. Pathology Findings: No increased neoplasm incidences in male or female rats were attributed to t-butylhydroquinone exposure. The incidences of mammary gland fibroadenoma and fibroadenoma or adenoma (combined) were significantly decreased in males exposed to 1,250 ppm and in all exposed groups of females; and combined incidences of mammary gland fibroadenoma, adenoma, or carcinoma were significantly decreased in all groups of exposed females. The decreases occurred with significant negative trends. Incidences of renal cysts and inflammation were generally increased in exposed groups of male rats. 2-YEAR STUDY IN MICE: Groups of 60 male and 60 female mice received 0, 1,250, 2,500, or 5,000 ppm t-butylhydroquinone in feed for 104 to 105 weeks. These exposure concentrations resulted in daily doses of approximately 150, 300, or 600 mg t-butylhydroquinone/kg body weight (males) or 150, 300, or 700 mg/kg (females). As many as 10 males and 10 females from each exposure group were evaluated at 15 months. Survival, Body Weights and Feed Consumption: Survival of all exposed groups of males and females was similar to that of the control groups. Mean body weights of the 5,000 ppm groups were generally lower than those of the control groups from week 13 until the end of the study. Feed consumption by exposed groups of males and females was similar to that by the controls. There were no biologically significant differences in clinical pathology parameters between control and exposed groups of mice. Pathology Findings: No increased incidences of neoplasms or nonneoplastic lesions in male or female mice were considered to be related to t-butylhydroquinone exposure. GENETIC TOXICOLOGY: t-Butylhydroquinone was not mutagenic in any of four strains of Salmonella typhimurium, with or without liver S9 metabolic activation enzymes. It did, however, induce sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells in the presence, but not the absence, of S9. No increase in the frequency of micronucleated erythrocytes was observed in bone marrow of male mice treated with t-butylhydroquinone. CONCLUSIONS: Under the conditions of this long-term feed study, there was no evidence of carcinogenic activity of t-butylhydroquinone in male or female F344/N rats exposed to 1,250, 2,500, or 5,000 ppm. Under the conditions of this 2-year feed study, there was no evidence of carcinogenic activity of t-butylhydroquinone in male or female B6C3F(1) mice exposed to 1,250, 2,500, or 5,000 ppm. Exposure of rats to t-butylhydroquinone in feed resulted in decreased incidences of mammary gland neoplasms in males and females. Synonyms: Tert-butyl-hydroquinone; 2-(1,1-dimethylethyl)-1,4-benzenediol; 2-tert-butylhydroquinone; mono-tert-butylhydroquinone; tert-butyl-1,4-benzenediol: mono-tertiarybutylhydroquinone; 2-tert-butyl-1,4-benzenediol; 2-(1,1-dimethyl)hydroquinone; 2-(tert-butyl)-p-hydroquinone; TBHQ; MTBHQ Trade Names: Sustane; Tenox TBHQ; Banox 20BA
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PMID:NTP Toxicology and Carcinogenesis Studies of t-Butylhydroquinone (CAS No. 1948-33-0) in F344/N Rats and B6C3F(1) Mice (Feed Studies). 1258 17

1,2-Dihydro-2,2,4-trimethylquinoline (monomer) is used as an antioxidant in styrene-butadiene and nitrile-butadiene rubbers and latexes. It was nominated by the National Cancer Institute as part of a review of chemicals used in the manufacture and processing of rubber, during which potential occupational and consumer exposure to this compound can occur. It was selected for evaluation because it is a derivative of quinoline, a known rodent carcinogen, and was regarded as having potential carcinogenic activity. Because of the pattern of use and exposure, dermal administration was considered most appropriate. Male and female F344/N rats and B6C3F1 mice received topical applications of 1,2-dihydro-2,2,4-trimethylquinoline in acetone (greater than 90% pure) for 13 weeks or 2 years. Groups of female SENCAR mice received 1,2-dihydro-2,2,4-trimethylquinoline (greater than 90% pure) during a 1-year dermal initiation/promotion study to determine the tumor initiation or promotion potential of the chemical. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood cells. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were topically administered 0, 5, 20, 50, 100, or 200 mg 1,2-dihydro-2,2,4-trimethylquinoline/kg body weight in acetone, 5 days per week for 13 weeks. In addition, there were 10 male and 10 female untreated controls. All rats survived to the end of the study. Final mean body weights and mean body weight gains of treated male and female rats were similar to those of the vehicle controls except those of 200 mg/kg males, which were significantly lower than those of the vehicle controls. The only notable clinical observation was skin discoloration of treated rats. In the 200 mg/kg groups, absolute and relative liver weights of males and absolute liver weights of females were significantly greater than those of the vehicle controls. There were no significant differences in hematology or clinical chemistry parameters, reproductive tissue parameters, or estrous cycle characterization between treated and control groups. Histopathologic lesions of the skin at the site of application included acanthosis and hyperkeratosis in 100 and 200 mg/kg males and 200 mg/kg females. Cytoplasmic vacuolization of hepatocytes of mild to moderate severity was observed in the livers of all 200 mg/kg males and was considered treatment related. Based on the incidence and severity of skin and liver lesions observed in 200 mg/kg rats in the 13-week study, 100 mg/kg was selected as the high dose for the 2-year rat study. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were topically administered 0, 2.5, 5, 10, 20, or 50 mg 1,2-dihydro-2,2,4-trimethylquinoline/kg body weight in acetone, 5 days per week for 13 weeks. In addition, there were 10 male and 10 female untreated controls. All mice except one 2.5 mg/kg female survived to the end of the study. Final mean body weights and mean body weight gains of male and female mice were similar to those of the vehicle controls. There were no treatment-related clinical observations. There were no significant differences between treated and control groups in organ weights, hematology and clinical chemistry parameters, reproductive tissue parameters, or estrous cycle characterization. Histopathologic lesions of the skin at the site of application included acanthosis (epidermal hyperplasia), hyperkeratosis, and parakeratosis, all ranging from minimal to mild in severity. Minimal to mild fibrosis and subchronic inflammation were observed in the dermis. Based on the incidences and severities of skin lesions observed in 20 and 50 mg/kg mice in the 13-week study, 10 mg/kg was selected as the high dose for the 2-year mouse study. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female F344/N rats were topically administered 0, 36, 60, or 100 mg 1,2-dihydro-2,2,4-trimethylquinoline/kg body weight in acetone, 5 days per week for 103 (males) or 104 (females) weeks. Ten rats per group were evaluated after 15 moed after 15 months of treatment. Survival and Body Weights Survival of treated rats was similar to that of controls. Mean body weights of 60 mg/kg males and 100 mg/kg males and females were slightly lower than those of the controls after week 21. Mean body weights of 36 mg/kg males and females and 60 mg/kg females were generally similar to those of the controls throughout the study. Pathology Findings: No skin neoplasms were attributed to treatment with 1,2-dihydro-2,2,4-trimethylquinoline. Several nonneoplastic skin lesions were determined to be treatment related. Incidences of acanthosis at the site of application in all treated groups of males and in 100 mg/kg females at the 15-month interim evaluation were significantly greater than those in the controls. At the end of the 2-year study, incidences of acanthosis at the site of application in 60 and 100 mg/kg males and females and hyperkeratosis at the site of application in 60 mg/kg females were significantly greater than those in the controls. Absolute and relative right kidney weights of 60 and 100 mg/kg male rats were significantly greater than those of the controls at the 15-month interim evaluation. Incidences of renal tubule adenoma and adenoma or carcinoma (combined) in all treated groups of males were significantly greater than those in the controls. These incidences exceeded the range from the historical controls in 2-year NTP feed studies. An extended (step section) evaluation of the kidneys of male rats did not reveal an additional increase in neoplastic response because additional adenomas and hyperplasias were observed in the controls as well as in treated groups. 2-YEAR STUDY IN MICE: Groups of 60 male and 60 female B6C3F1 mice were topically administered 0, 3.6, 6, or 10 mg 1,2-dihydro-2,2,4-trimethylquinoline/kg body weight in acetone, 5 days per week for 103 (males) or 104 (females) weeks. Nine or ten mice per group were evaluated after 15 months of treatment. Survival and Body Weights: Survival of treated mice was similar to that of controls. Mean body weights of treated male and female mice were similar to those of the controls throughout the study. Pathology Findings: No neoplasms or nonneoplastic lesions were attributed to treatment with 1,2-dihydro-2,2,4-trimethylquinoline. 1-YEAR INITIATION/PROMOTION STUDY IN FEMALE SENCAR MICE: Groups of 30 female SENCAR mice were topically administered varying initiation/promotion treatments as outlined in the table below. Survival, Body Weights, and Clinical Findings: Survival in all treated groups was similar to that of the respective controls, except in the 2.5 mg 7,12-dimethylbenz(a)anthracene (DMBA)/0.5 mg 12-O-tetradecanoylphorbol-13-acetate (TPA) group in which survival was significantly lower than that of the controls. Mean body weights of all treated groups were similar to those of the respective controls throughout the study. No clinical observations were associated with 1,2-dihydro-2,2,4-trimethylquinoline treatment; however, mice promoted with TPA showed signs of irritation and papilloma at the site of application. Pathology Findings: Initiation and promotion with acetone alone was not associated with any skin lesions at the site of application. The incidences of acanthosis and chronic inflammation were increased in all groups promoted with TPA regardless of the initiator treatment; however, the incidences of nonneoplastic lesions were low in all other groups. Incidences of squamous cell papillomas and squamous cell carcinomas were markedly increased in the DMBA/TPA positive control group; however, no response was observed in groups initiated with DMBA and promoted with 5, 10, or 25 mg/kg 1,2-dihydro-2,2,4-trimethylquinoline or in the group initiated with 1,2-dihydro-2,2,4-trimethylquinoline and promoted with TPA. GENETIC TOXICOLOGY: 1,2-Dihydro-2,2,4-trimethylquinoline was not mutagenic in any of several strains of Salmonella typhimurium, with or without S9 metabolic activation. 1,2-Dihydro-2,2,4-trimethylquinoline induced sister chromatid exchanges in cultured Chinese hamster ovary cells in the absence of S9, but not in the presence of S9. However, no increase in the frequency of chromosomal aberrations was observed in cultured Chinese hamster ovary cells treated with 1,2-dihydro-2,2,4-trimethylquinoline, with or without S9. No increase in the frequency of micronucleated erythrocytes was noted in peripheral blood of male or female mice exposed topically to 1,2-dihydro-2,2,4-trimethylquinoline for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year dermal studies, there was some evidence of carcinogenic activity of 1,2-dihydro-2,2,4-trimethylquinoline in male F344/N rats, based on increased incidences of renal tubule adenoma and adenoma or carcinoma (combined). There was no evidence of carcinogenic activity of 1,2-dihydro-2,2,4-trimethylquinoline in female F344/N rats receiving 36, 60, or 100 mg/kg, or in male or female B6C3F1 mice receiving 3.6, 6, or 10 mg/kg. Exposure of rats to 1,2-dihydro-2,2,4-trimethylquinoline by dermal application in acetone for 2 years resulted in acanthosis in males and females and hyperkeratosis in females at the site of application. No nonneoplastic lesions in male or female mice were attributed to treatment with 1,2-dihydro-2,2,4-trimethylquinoline. Synonyms: 2,2,4-Trimethyl-1,2-dihydroquinoline; acetone anil; methylquinoline Trade names: Agerite Resin D; Flectol A; Flectol H; Flectol Pastilles; Vulkanox HS/LG; Vulkanox HS/Powder
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PMID:NTP Toxicology and Carcinogenesis Studies of 1,2-Dihydro-2,2,4-Trimethylquinoline (CAS No. 147-47-7) in F344/N Rats and B6C3F1 Mice (Dermal Studies) and the Dermal Initiation/Promotion Study in Female Sencar Mice. 1258 20

Nickel subsulfide is used in the manufacture of lithium batteries and is a major component in the refining of certain nickel ores. Nickel subsulfide was nominated as part of a class study of nickel compounds, for which there was little information on the toxic and carcinogenic effects of inhalation exposure. Male and female F334/N rats and B6C3F1 mice were exposed to nickel subsulfide (at least 97% pure; the mean value for the mass median aerodynamic diameter at each exposure concentration ranged from 2.0 to 2.2 mm by inhalation 6 hours per day, 5 days per week, for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, and mouse peripheral blood samples were analyzed for frequency of micronucleated normochromatic erythrocytes. 16-DAY STUDY IN RATS: Groups of five male and five female F344/N rats were exposed to atmospheres containing 0, 0.6, 1.2, 2.5, 5, or 10 mg nickel subsulfide/m(3) (equivalent to 0, 0.44, 0.88, 1.83, 3.65, and 7.33 mg nickel/m(3)) 6 hours per day, 5 days per week for a total of 12 exposure days during a 16-day period. Additionalmgroups of three male and three female rats were exposed to 0, 0.6, 2.5, or 10 mg/m(3) for tissue burden studies. One male exposed to 10 mg nickel subsulfide/m(3) in the core study died on day 14; all other rats survived until the end of the study. Final mean body weights and mean body weight gains of males exposed to 5 or 10 mg nickel subsulfide/m(3) and females exposed to 2.5, 5, or 10 mg/m(3) were significantly lower than those of the controls. Clinical findings of toxicity on day 5 of the study included labored respiration in 10 mg/m(3) males and 5 and 10 mg/m(3) females and dehydration in 5 and 10 mg/m(3) females. Absolute and relative lung weights of 2.5, 5, and 10 mg/m(3) males and all exposed groups of females were significantlymgreater than those of the controls, as was the absolute lung weight of 1.2 mg/m(3) males. Inflammation of the lung and atrophy of the nasal olfactory epithelium occurred in all exposed mgroups. The concentrations of nickel in the lungs of exposedmgroups of rats increased with exposure concentration (males, 7 to 67 mg nickel/g lung; females, 9 to 77 mg/g lung). 16-DAY STUDY IN MICE: Groups of five male and five female B6C3F1 mice were exposed to atmospheres containing 0, 0.6, 1.2, 2.5, 5, or 10 mg nickel subsulfide/m(3) for 6 hours per day, 5 days per week for a total of 12 exposure days during a 16-day period. Additional groups of three male and three female mice were exposed to 0, 0.6, 2.5, or 10 mg/m(3) for tissue burden studies. All male and female mice exposed to 10 mg nickel subsulfide/m(3) in the core study died before the end of the study; the death of one female was accidental. One control male, one control female, and one 1.2 mg/m(3) male also died before the end of the study. Final mean body weights and mean body weight gains of 5 mg/m(3) males were significantly lower than those of the controls. Clinical findings at day 5 included labored respiration in 10 mg/m(3) males and females. The absolute lung weight of 5 mg/m(3) males, the absolute and relative lung weights of 10 mg/m(3) males and 5 mg/m(3) females, and the relative lung weight of 10 mg/m(3) females were significantly greater than those of the controls. Inflammation of the lung occurred in 2.5, 5, and 10 mg/m(3) male and female mice, fibrosis of the lung occurred in 5 mg/m(3) males and females, and lymphoid hyperplasia of the bronchial lymph nodes and atrophy of the nasal olfactory epithelium occurred in 1.2, 2.5, 5, and 10 mg/m(3) males and females. Nickel concentrations in the lung of exposed male and female mice were greater than those of the controls (males, 10 to 20 mg nickel/g lung; females, 8 to 20 mg/g lung) 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were exposed to atmospheres containing 0, 0.15, 0.3, 0.6, 1.2, or 2.5 mg nickel subsulfide/m(3) (equivalent to 0, 0.11, 0.22, 0.44, 0.88, and 1.83 mg nickel/m(3)) 6 hours per day, 5 days per week for 13 weeks. Additional groups of 18 male and 18 female female rats were exposed to 0, 0.15, 0.6, or 2.5 mg/m(3) for tissue burden studies. All core study rats survived until the end of the study. Final mean body weights and mean body weight gains of 2.5 mg/m(3) males were significantly lower than those of the controls; final mean body weights of all other exposure groups were similar to those of the controls. Chemical-related clinical findings included labored respiration in 2.5 mg/m(3) males and females during weeks 2 through 7. In general, neutrophil and erythrocyte counts, hematocrit values, and hemoglobin concentrations were minimally increased in exposed rats. Absolute and relative lung weights of all exposed groups were significantly greater than those of the controls. Increases in the number of alveolar macrophages, interstitial infiltrates, or incidences of chronic inflammation of the lung occurred in all groups exposed to nickel subsulfide concentrations of 0.3 mg/m(3) or greater; the severity of these lesions generally increased with increasing exposure concentration. Increases in the number of alveolar macrophages were observed in 0.15 mg/m(3) males and females. Lymphoid hyperplasia of the bronchial and mediastinal lymph nodes was observed in rats exposed to 0.3 mg/m(3) or greater. Most 0.6, 1.2, and 2.5 mg/m(3) males and females had atrophy of the nasal olfactory epithelium, and the severity generally increased with increasing exposure concentration. Nickel concentrations in the lung increased with exposure concentration and were greater than those in the controls in rats exposed for 13 weeks (males, 5 to 18 mg nickel/g lung; females, 5 to 17 mg/g lung). 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to atmospheres containing 0, 0.15, 0.3, 0.6, 1.2, or 2.5 mg nickel subsulfide/m(3) for 6 hours per day, 5 days per week for 13 weeks. Additional groups of six male and six female mice were exposed to 0, 0.15, 0.6, or 2.5 mg/m(3) for tissue burden studies. Final mean body weights of all exposure groups were similar to those of the controls. No chemical-related clinical findings were observed. Lymphocyte counts in 1.2 and 2.5 mg/m(3) males were minimally greater than that of the controls. Hemoglobin concentrations and erythrocyte counts in 0.3, 0.6, 1.2, and 2.5 mg/m(3) females were minimally greater than those of the controls. Absolute and relative lung weights of 1.2 and 2.5 mg/m(3) males and females were significantly greater than those of the controls. An increase in alveolar macrophages was present in mice from the 0.3 mg/m(3) and higher exposure groups. Chronic inflammation and fibrosis were observed in the lung of 1.2 and 2.5 mg/m(3) males and females. Interstitial infiltrates of lymphocytes were observed in mice exposed to 0.6, 1.2, or 2.5 mg/m(3). Lymphoid hyperplasia of the bronchial lymph nodes was observed in groups exposed to 1.2 or 2.5 mg/m(3). Atrophy of the nasal olfactory epithelium occurred in 0.6, 1.2, and 2.5 mg/m(3) males and females, and incidences and severity generally increased with increasing exposure concentration. At 13 weeks, nickel concentrations in the lungs of exposed mice were greater than those of the controls (males, 3 to 17 g nickel/g lung; females, 6 to 23 mg/g lung), and these concentrations increased with increasing exposure concentration. 2-YEAR STUDY IN RATS: Survival, Body Weights, Clinical Findings, and Hematology: Groups of 63 male and 63 female F344/N rats were exposed to 0, 0.15, or 1 mg nickel subsulfide/m(3) (equivalent to 0, 0.11, or 0.73 mg nickel/m(3)) by inhalation for 6 hours per day, 5 days per week for 104 weeks. Survival of exposed males and female rats was similar to that of the controls. Mean body weights of males and females exposed to 0.15 mg/m(3) were similar to those of the controls. Mean body weights of rats exposed to 1 mg/m(3) were lower than those of the controls throughout the second year of the study. Chemical-related clinical findings included rapid and shallow breathing following exposure periods. Hematocrit values and hemoglobin concentrations in 1 mg/m(3) males and females and the erythrocyte count in 1 mg/m(3) males were mildly greater than those in the controls. Pathology Findings: In general, the absolute and relative lung weights of exposed males and females were significantly greater than those of the controls at 7 and 15 months. There were exposure-related increases in the incidences of alveolar/bronchiolar adenoma in males, alveolar/bronchiolar carcinoma in males and females, and alveolar/bronchiolar adenoma or carcinoma (combined) in males and females at 2 years. Nonneoplastic lung lesions generally observed in exposed males and females included fibrosis; chronic active inflammation; focal alveolar epithelial hyperplasia, macrophage hyperplasia, and proteinosis; bronchial lymphoid hyperplasia; and interstitial inflammation. At 2 years, there were significant exposure-related increases in the incidences of benign pheochromocytoma, malignant pheochromocytoma, and benign or malignant pheochromocytoma (combined) in males and of benign pheochromocytoma in females. The incidence of adrenal medulla hyperplasia in 1 mg/m(3) females was significantly greater than that of the controls At 2 years, the incidences of chronic active inflammation of the nose in 1 mg/m(3) females and of olfactory epithelial atrophy in 1 mg/m(3) males and females were significantly greater than those of the controls. The incidences of lymphoid hyperplasia of the bronchial lymph node in exposed males at 7 and 15 months and in exposed males and females at 2 years were significantly greater than those of the controls. Incidences of macrophage hyperplasia in the bronchial lymph node of exposed males at 15 months and exposed males and females at 2 years were greater than those of the controls. Tissue Burden Analyses: Nickel concentrations in the lungs of exposed rats were greater than those of the controls at 7 months (males, 6 to 9 mg nickel/g lung; females, 6 to 9 mg/g lung) and 15 months (males, 4 to 3 mg nickel/g lung; females, 4 to 7 mg/g lung). 2-YEAR STUDY IN MICE: Survival, Body Weights, Clinical Findings, and Hematology: Groups of 80 male and 80 female B6C3F1 mice were exposed to 0, 0.6, or 1.2 mg nickel subsulfide/m(3) (equivalent to 0, 0.44, or 0.88 mg nickel/m(3)) by inhalation for 6 hours per day, 5 days per week for 105 weeks. Survival of exposed male and female mice was similar to that of the controls. Mean body weights of 0.6 and 1.2 mg/m(3) males and females were less than those of the controls throughout the second year of the study. Chemical-related clinical findings in male and female mice included labored respiration following exposure periods. The hematocrit value and the segmented neutrophil, monocyte, lymphocyte, and total leukocyte counts in 1.2 mg/m(3) females were greater than those in the controls. Pathology Findings: Absolute and relative lung weights of exposed males and females were generally significantly greater than those of the controls at 7 and 15 months. The incidence of alveolar/bronchiolar carcinoma in 0.6 mg/m(3) females and the incidences of alveolar/bronchiolar adenoma or carcinoma (combined) in 0.6 mg/m(3) males and 0.6 and 1.2 mg/m(3) females were significantly less than those of the controls. In general, the incidences of chronic active inflammation; bronchialization (alveolar epithelial hyperplasia), macrophage hyperplasia and proteinosis; interstitial infiltration; and fibrosis in exposed groups of males and females were greater than those of the controls at 7 and 15 months and at 2 years. The incidences of atrophy of the nasal olfactory epithelium and inflammation of the nose in exposed mice were also generally greater than those of the controls. At 2 years, the incidences of degeneration of olfactory epithelium in exposed females were significantly less than that of the controls. The incidences of lymphoid hyperplasia of the bronchial lymph node in 1.2 mg/m(3) males at 15 months, in 0.6 and 1.2 mg/m(3) females at 15 months, and in 0.6 and 1.2 mg/m(3) males and females at 2 years were significantly greater than those of the controls. The incidences of macrophage hyperplasia in 1.2 mg/m(3) males at 7 and 15 months, in 0.6 and 1.2 mg/m(3) females at 15 months, and in 0.6 and 1.2 mg/m(3) males and females at 2 years were significantly greater than those of the controls. Tissue Burden Analyses: Nickel concentrations in the lungs of exposed mice were greater than those of the controls at 7 months (males, 10 to 11 mg nickel/g lung; females, 10 to 14 mg/g lung) and 15 months (males, 12 to 20 mg nickel/g lung; females, 15 to 26 mg/g lung). GENETIC TOXICOLOGY: Nickel subsulfide was considered to be equivocal in the Salmonella gene mutation assay overall. Sporadic weakly positive and equivocal responses were obtained in strain TA100 with and without S9 metabolic activation enzymes; all other strain/activation combinations gave negative results. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood samples from male or female mice exposed to nickel subsulfide by inhalation for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was clear evidence of carcinogenic activity of nickel subsulfide in male F344/N rats based on increased incidences of alveolar/bronchiolar adenoma, carcinoma, and adenoma or carcinoma (combined) and on increased incidences of benign, malignant, and benign or malignant (combined) pheochromocytoma of the adrenal medulla. There was clear evidence of carcinogenic activity of nickel subsulfide in female F344/N rats based on increased incidences of alveolar/bronchiolar carcinoma and alveolar/bronchiolar adenoma or carcinoma (combined) and an increased incidence of benign pheochromocytoma of the adrenal medulla. There was no evidence of carcinogenic activity of nickel subsulfide in male or female B6C3F1 mice exposed to 0.6 or 1.2 mg/m(3). Exposure of male and female rats to nickel subsulfide by inhalation for 2 years resulted in inflammation, hyperplasia, and fibrosis in the lung; inflammation and atrophy of the olfactory epithelium in the nose; and hyperplasia in the adrenal medulla (females). Exposure of male and female mice to nickel subsulfide by inhalation for 2 years resulted in inflammation, bronchialization, hyperplasia, and fibrosis in the lung and inflammation and atrophy of the olfactory epithelium in the nose. Synonyms: Heazlewoodite, nickel subsulphide, nickel sulfide (3:2), a-nickel sulfide (3:2) crystalline, nickel sulphide, nickel tritadisulphide, trinickel disulfide
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PMID:NTP Toxicology and Carcinogenesis Studies of Nickel Subsulfide (CAS No. 12035-72-2) in F344 Rats and B6C3F1 Mice (Inhalation Studies). 1259 22


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