Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0002871 (anemia)
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Acetonitrile is used primarily as a solvent in extractive distillation and crystallization of pharmaceutical and agricultural products and as a catalyst in chemical reactions. It was nominated for testing by the National Cancer Institute due to its presence in drinking water supplies and the environment, due to lack of information on the carcinogenicity of alkyl cyanides, and because of widespread worker exposure. Male and female F344/N rats and B6C3F1 mice were exposed to acetonitrile (at least 99% pure) by inhalation for 13 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and peripheral blood of B6C3F1 mice exposed to acetonitrile for 13 weeks. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were exposed to 0, 100, 200, 400, 800, or 1,600 ppm (equivalent to 0, 168, 335, 670, 1,340, or 2,681 mg/m(3)) acetonitrile by inhalation for 6 hours per day, 5 days per week for 13 weeks. Six male and three female rats that received 1,600 ppm and one male that received 800 ppm died during the study. At exposure concentrations up to and including 800 ppm, the final mean body weights and body weight gains were generally similar to those of the controls. At 1,600 ppm, body weight gain was lower and the final mean body weights of both males and females were significantly lower than those of the controls. Hypoactivity and ruffled fur were observed during the first week of the study in males receiving 800 ppm and males and females receiving 1,600 ppm. Additional clinical findings in 1,600 ppm males that died during week 1 were ataxia, abnormal posture, and clonic convulsions. Clinical pathology findings included nonresponsive, normocytic, normochromic anemia in 1,600 ppm males and females and in 800 ppm females, and decreased triiodothyronine (T3) concentrations in 1,600 ppm females. Absolute and relative thymus weights were significantly lower than those of the controls in the 800 and 1,600 ppm males and females. Females exposed to 1,600 ppm had significantly greater absolute and relative heart, kidney, and liver weights than those of the controls. There were no clear exposure-related histopathologic effects, although pulmonary congestion and edema and hemorrhage in the lung and brain were seen in some rats that died early. These lesions are consistent with cyanide-induced anoxia. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to 0, 100, 200, 400, 800, or 1,600 ppm (equivalent to 0, 168, 335, 670, 1,340, or 2,681 mg/m(3)) acetonitrile by inhalation for 6 hours per day, 5 days per week for 13 weeks. All mice exposed to 1,600 ppm died during the first 3 weeks of the study. In addition, one 400 ppm female and one male and four females from the 800 ppm groups also died before the end of the study. Body weight gains were similar to those of controls for all surviving groups of mice except the 800 ppm males, for which the final mean body weight was slightly lower than that of the controls. Clinical findings observed during the first week in 800 and 1,600 ppm mice were hypoactivity and a hunched, rigid posture. In males that received 200 ppm and above, absolute liver weights were greater than that of the controls and relative liver weights were greater in all exposed groups. In 800 ppm females, the absolute liver weight was greater than that of the controls and relative liver weights of females that received 400 ppm and above were greater than that of the controls. Lesions clearly associated with acetonitrile exposure were observed in the stomach, predominantly the forestomach, of males that received 400 ppm and above and of females that received 200 ppm and above. Histologically, these focal or multifocal pale to dark raised lesions consisted of areas of focal epithelial hyperplasia and ulceration, sometimes associated with hemosiderin deposition. An increased incidence of cytoplasmic vacuolation occurred in the liver of males and females exposed to 400 or 800 ppm. A lack of fatty degenerative change was observed inrved in the X-zone of the adrenal cortex of 800 and 1,600 ppm female mice. 2-YEAR STUDY IN RATS: The doses selected for the 2-year study of acetonitrile were based on reduced survival of 800 ppm males and 1,600 ppm males and females in the 13-week study. Groups of up to 56 male and 56 female rats were exposed to 0, 100, 200, or 400 ppm (equivalent to 0, 168, 335, or 670 mg/m(3)) acetonitrile by inhalation for 6 hours per day, 5 days per week for 2 years. Eight male and eight female rats from each exposure group were evaluated at 15 months for histopathology and hematology parameters. Survival, Body Weights, Clinical Findings, and Hematology: Two-year survival, mean body weights, organ weights, behavior, general health, and appearance of exposed male and female rats were similar to those of the controls. The hematologic effects observed were minor and of no biological significance. Pathology Findings: The incidences of hepatocellular adenoma (3/48), hepatocellular carcinoma (3/48), and hepatocellular adenoma or carcinoma (combined; 5/48) were greater in male rats exposed to 400 ppm than in the controls (one carcinoma). The incidences of hepatocellular adenoma and hepatocellular carcinoma were within the range of historical controls. However, the incidence of hepatocellular adenoma or carcinoma (combined) slightly exceeded the range of historical controls (2%-8%). In addition, the incidences of basophilic, eosinophilic, and mixed cell foci in 400 ppm males were marginally greater than in controls, suggesting hepatotoxicity of acetonitrile. There were no exposure-related liver lesions in female rats. 2-YEAR STUDY IN MICE: The exposure concentrations selected for the 2-year study were based on reduced survival and gross and histopathologic lesions in 400, 800, and 1,600 ppm groups of male and female mice in the 13-week study. Groups of 60 male and 60 female mice were exposed to 0, 50, 100, or 200 ppm (equivalent to 0, 84, 168, or 335 mg/m(3)) acetonitrile by inhalation for 6 hours per day, 5 days per week for 2 years. Ten male and 10 female mice from each exposure group were evaluated at 15 months for histopathology. Survival, Body Weights, and Clinical Findings: Two-year survival of exposed male and female mice was similar to that of the controls, except that the survival of male mice in the 200 ppm group was significantly greater than that of the controls. Mean body weights and organ weights of exposed groups of male and female mice were similar to those of the controls, and no clinical observations in any group were clearly related to acetonitrile exposure. Pathology Findings: There were no increases in the incidences of neoplasms that were considered related to acetonitrile exposure in mice. The incidence of squamous hyperplasia of the epithelium of the forestomach was significantly increased at 15 months in 200 ppm females. At 2 years, the increased incidence of this lesion was dose related in all exposed groups of males and females. GENETIC TOXICOLOGY: Acetonitrile was not mutagenic in Salmonella typhimurium strain TA97, TA98, TA100, TA1535, or TA1537, with or without S9 metabolic activation. In cultured Chinese hamster ovary cells, acetonitrile produced a weakly positive response in the sister chromatid exchange test without, but not with, S9. A small increase in chromosomal aberrations was observed in cultured Chinese hamster ovary cells treated with acetonitrile in the presence, but not in the absence, of S9. A significant increase in micronucleated normochromatic erythrocytes was observed in peripheral blood samples from male mice treated with acetonitrile for 13 weeks; the frequency of micronucleated erythrocytes in female mice was not affected by exposure to acetonitrile. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was equivocal evidence of carcinogenic activity of acetonitrile in male F344/N rats based on marginally increased incidences of hepatocellular adenoma and carcinoma. There was no evidence of carcinogenic activity of acetonitrile in female F344/N rats exposed to 100, 200, or 400 ppm. There was no evidence of carcinogenic activity of acetonitrile in male or female B6C3F1 mice exposed to 50, 100, or 200 ppm. Exposure to acetonitrile by inhalation resulted in increased incidences of hepatic basophilic foci in male rats and of squamous hyperplasia of the forestomach in male and female mice. Synonyms: Cyanomethane, ethanenitrile, ethyl nitrile, methanecarbonitrile, methyl cyanide, nitrile of acetic acid
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PMID:NTP Toxicology and Carcinogenesis Studies of Acetonitrile (CAS No. 75-05-8) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). 1259 28

Scopolamine hydrobromide trihydrate is used in ophthalmic preparations and as a preanesthetic sedative. Its major use is in transdermal patches for the treatment of motion sickness. Scopolamine hydrobromide trihydrate was selected for study because of considerable human exposure resulting from its use in prescription and over-the-counter preparations. Scopolamine was a suspect carcinogen because it contains an aliphatic epoxide moiety which may act as a biological alkylating agent. Male and female F344/N rats and B6C3F1 mice received scopolamine hydrobromide trihydrate (89% pure) in distilled water by gavage for 16 days, 14 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes. 16-DAY STUDY IN RATS: Groups of five male and five female rats were administered 0, 75, 150, 300, 600, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 16 days. All rats survived to the end of the study. The final mean body weights and body weight gains of males receiving 600 and 1,200 mg/kg and the mean body weight gain of males receiving 300 mg/kg were significantly lower than those of the control group. Clinical findings included bilateral pupillary dilation in all dosed animals and red eyelids in males and females receiving 1,200 mg/kg. There were no significant treatment-related gross or microscopic lesions. 16-DAY STUDY IN MICE: Groups of five male and five female mice were administered 0, 150, 250, 450, 900, or 1,800 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 16 days. One male and two females receiving 1,800 mg/kg and one female receiving 150 mg/kg died during the study. The final mean body weights and body weight gains of dosed mice were similar to those of the control groups. Clinical findings related to scopolamine hydrobromide trihydrate administration included bilateral pupillary dilation and squinting in all dosed males and females. The relative liver weights of males receiving 1,800 mg/kg and of females in all dosed groups were significantly greater than those of the control groups. There were no significant treatment-related gross or microscopic lesions. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were administered 0, 15, 45, 135, 400, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 14 weeks. One female receiving 45 mg/kg, one male and one female receiving 135 mg/kg, six males and one female receiving 400 mg/kg, and eight males and seven females receiving 1,200 mg/kg died during the study. The final mean body weights and mean body weight gains of all dosed males and females were significantly lower than those of the control groups. Clinical findings included bilateral pupillary dilation in all dosed males and females and reddening of the eyes in 15 mg/kg males and 135, 400, and 1,200 mg/kg males and females. Hematocrit, hemoglobin concentration, and/or erythrocyte count in male and female rats receiving 45 mg/kg or greater were slightly higher than those of the control groups. In general, these changes were most prominent in rats in the 400 and 1,200 mg/kg groups. Higher hematocrit, hemoglobin concentration, and erythrocyte count were likely due to hemoconcentration from dehydration (relative erythrocytosis). A minimal to mild mature neutrophilia, evidenced by higher segmented neutrophil numbers than in the control group, occurred in all dosed male rats. Sperm morphology and vaginal cytology parameters in dosed rats were similar to those in the control groups. Nine male and five female dosed rats died from esophageal obstructions consisting of feed and bedding material in the posterior pharynx. Tracheal obstruction occurred concurrently with esophageal obstruction as a result of food build-up in the oropharyngeal region. This condition is considered to be secondary to the inhibitory effects of scopolamine hydrobromide trihydrate on salivary gland secretions and on esopon esophageal smooth muscle involved in swallowing. There were no other significant treatment-related gross or microscopic findings. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were administered 0, 15, 45, 135, 400, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 14 weeks. One male receiving 135 mg/kg and two males and one female receiving 1,200 mg/kg died during the study. The final mean body weights and mean body weight gains of all dosed male groups and females receiving 45 mg/kg and above were significantly lower than those of the control groups. Clinical observations included bilateral pupillary dilation, hyperactivity, and hypoactivity. A minimal to mild mature neutrophilia, similar to that which occurred in the 14-week rat study, occurred in male mice receiving 45 mg/kg or greater. As in the rat study, there was no microscopic evidence of inflammation that could account for the neutrophilia. The estrous cycle length of 1,200 mg/kg females was significantly greater than that in the control group. There were no significant treatment-related gross or microscopic lesions. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female rats were administered 0, 1, 5, or 25 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 104 weeks. Ten males and ten females from each dose group, excluding the 1 mg/kg female group, were evaluated at 15 months. Survival, Body Weights, Clinical Findings, and Ophthalmic Examination Findings: The survival rates of female rats receiving 1 and 25 mg/kg were significantly lower than that of the control group. Mean body weights of 1 and 5 mg/kg males and females were similar to those of the controls throughout the study. However, mean body weights of 25 mg/kg males and females were generally lower than those of the control groups after about week 25. Clinical findings included bilateral pupillary dilation in all dosed males and females. Ophthalmic examination revealed no significant findings. Hematology: Compared to controls, hematocrit was slightly higher in the 25 mg/kg male rats, similar to the effects observed in the 14-week study; this is consistent with dehydration resulting in hemoconcentration. Reticulocyte numbers in the 25 mg/kg female rats were slightly lower than those in the controls. This result is consistent with the lower body weights, and thus a decreased nutritional status, exhibited by these animals. Plasma Scopolamine Determinations: The serum scopolamine concentrations were 6 ng scopolamine/mL serum for the 5 mg/kg female sample and 12 and 28 ng/mL for the 25 mg/kg male and female samples, respectively. The amounts of scopolamine in the other serum samples were below the minimum detection limit (4 ng/mL) of the analysis method. Neurobehavioral Findings: Horizontal motor activity of 25 mg/kg females was significantly greater than that of the control group on days 90, 180, and 360. Startle response of 5 and 25 mg/kg females was significantly lower than that of the control group on day 90. On day 180, passive avoidance of 25 mg/kg males was significantly lower than that of the control group. Pathology Findings: The incidences of adenoma of the pituitary gland pars distalis decreased with increasing dose in both male and female rats; however, this trend was only significant in males (males: vehicle control, 19/49; 1 mg/kg, 17/49; 5 mg/kg, 13/50; 25 mg/kg, 10/50; females: 20/50, 13/60, 14/50, 10/50). The incidences of adenoma of the pituitary gland pars distalis in 25 mg/kg males and all groups of dosed females were below the NTP historical control range. The incidences of hyperplasia were not significantly different from those in the control groups. The incidences of mononuclear cell leukemia in 25 mg/kg males and females were significantly lower than those of the control groups (males: 33/50, 21/50, 26/50, 24/50; females: 20/50, 6/60, 13/50, 4/50). The incidence of mononuclear cell leukemia in females receiving 25 mg/kg was well below the NTP historical range. 2-YEAR STUDY IN MICE: Groups of 70 male and 70 female mice were administered 0, 1, 5, or 25 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 104 to 105 weeks. Ten control animals and ten animals from each dose level were evaluated at 15 months. Survival, Body Weights, Clinical Findings, and Ophthalmic Examination Findings Survival of dosed males and females was similar to that of the controls. The mean body weights of males and females receiving 1 mg/kg were similar to those of the control groups throughout the majority of the study. The mean body weights of 5 mg/kg males and females were slightly lower than those of the controls. The mean body weights of males and females receiving 25 mg/kg were lower than those of the control groups after week 13. Clinical findings included bilateral pupillary dilation in all dosed male and female groups. Ophthalmic examination revealed no significant findings. Hematology: Hematocrit, hemoglobin concentration, and erythrocyte count in 25 mg/kg female mice were slightly lower than those in the control group. These results are consistent with development of a minimal normocytic, normochromic nonresponsive anemia. The anemia may be related to the lower body weights exhibited by these animals and are presumed to be due to a decreased nutritional status. Pathology Findings: The combined incidences of hepatocellular neoplasms (adenoma or carcinoma) occurred with a significant negative trend in males and females (males: vehicle control, 30/50; 1 mg/kg, 33/50; 5 mg/kg, 14/50; 25 mg/kg, 15/50; females: 22/51, 21/50, 16/50, 9/51). The combined incidences of hepatocellular neoplasms in 5 and 25 mg/kg males were within the NTP historical control range. The incidences of clear cell foci and eosinophilic foci in dosed male groups, and eosinophilic foci in 25 mg/kg females, were significantly lower than those of the control groups. The incidences of many spontaneously occurring nonneoplastic lesions were significantly lower in dosed mice than in the control groups and usually decreased with increasing dose. These included kidney nephropathy, alveolar epithelial hyperplasia, hyperplasia of the pancreatic islets, bone marrow myelofibrosis, hyperplasia of the pituitary gland pars distalis, cystic hyperplasia of the uterus, and hematopoietic cell proliferation of the spleen. The decreased incidences of these spontaneous lesions were most likely a result of lower body weights in dosed animals. GENETIC TOXICOLOGY: Scopolamine hydrobromide trihydrate did not induce mutations in any of five strains of Salmonella typhi murium, with or without S9 metabolic activation enzymes, nor did it induce sister chromatid exchanges in cultured Chinese hamster ovary cells, with or without S9. A weakly positive response was obtained, however, in a chromosomal aberrations test conducted in cultured Chinese hamster ovary cells with very high doses of scopolamine hydrobromide trihydrate in the presence of S9; without S9, no increase in aberrations was noted. Despite the evidence for chromosomal damage observed in vitro, no increase in the frequencies of micronucleated normochromatic erythrocytes was observed in peripheral blood samples of male or female mice exposed to scopolamine hydrobromide trihydrate for 14 weeks by gavage. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of scopolamine hydrobromide trihydrate in male or female F344/N rats or B6C3F1 mice administered 1, 5, or 25 mg/kg. Synonyms: Scopolamine hydrobromide, 6,7-epoxytropan-3-yl, euscopol, hydroscine hydrobromide, hyoscine bromide, (-)-hyoscine hydrobromide, hysco, isoscopil, scopolammonium bromide, (s)-tropate hydrobromide trihydrate, lα-tropyl-a-scopine
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PMID:NTP Toxicology and Carcinogenesis Studies of Scopolamine Hydrobromide Trihydrate (CAS No. 6533-68-2) in F344 Rats and B6C3F1 Mice (Gavage Studies). 1259 30

p-Nitrobenzoic acid is produced in large volumes for organic synthesis and as an intermediate in the manufacture of pesticides, dyes, and industrial solvents. Groups of male and female F344/N rats and B6C3F1 mice were exposed to p-nitrobenzoic acid (>99% pure) in feed for 14 days, 13 weeks, or 2 years for toxicity and carcinogenicity studies. Genetic toxicology studies were conducted in in vitro assays with Salmonella typhimurium and cultured Chinese hamster ovary cells, and in studies of erythrocyte micronucleus formation in mice in the 13-week study. 14-DAY STUDY IN RATS: Groups of five male and five female rats were given 0, 2,500, 5,000, 10,000, 20,000, or 40,000 ppm p-nitrobenzoic acid in feed for 14 days. All rats survived until the end of the study. Male and female rats given 20,000 and 40,000 ppm lost weight. The final mean body weights of 10,000, 20,000, and 40,000 ppm males were 82%, 60%, or 52% that of the controls, and the final mean body weights of 10,000, 20,000, and 40,000 ppm females were 87%, 68%, and 65% that of the controls. There were no clinical findings that were characteristic of organ-specific toxicity. Absolute and relative spleen weights were significantly increased in rats exposed to 10,000, 20,000, and 40,000 ppm. There were decreases in erythrocyte count and hemoglobin and hematocrit values and increases in reticulocyte count, nucleated erythrocytes, and methemoglobin concentration that were most pronounced in the 20,000 and 40,000 ppm groups. Congestion of the spleen occurred in 10,000 ppm males and in 20,000 and 40,000 ppm females. Hypertrophy of the follicular epithelium of the thyroid gland was present in male and female rats exposed to 10,000, 20,000, or 40,000 ppm p-nitrobenzoic acid, while follicular hyperplasia was observed in the 40,000 ppm males and females. Atrophy of the testis was observed in 20,000 and 40,000 ppm males. Other lesions observed in 20,000 and 40,000 ppm rats included atrophy of the thymus in males and atrophy of the ovary, bone marrow, and thymus in females. 14-DAY STUDY IN MICE: Groups of five male and five female mice were given 0, 2,500, 5,000, 10,000, 20,000, or 40,000 ppm p-nitrobenzoic acid in feed for 14 days. Three males and two females given 40,000 ppm died during the study. All other animals survived until the end of the study. Male mice given 20,000 and 40,000 ppm and females given 20,000 ppm lost weight. Mean body weight gains of 20,000 and 40,000 ppm males and 10,000, 20,000, and 40,000 ppm females were significantly lower than those of the controls. There were no clinical findings related to organ-specific toxicity although lethargy and ataxia were observed in 40,000 ppm mice. Relative liver weights were significantly increased in 20,000 and 40,000 ppm males and females and in 10,000 ppm females. Absolute and relative thymus weights of 20,000 and 40,000 ppm males and of 10,000, 20,000, and 40,000 ppm females were reduced. No significant differences in hematology parameters occurred in exposed mice. Testicular degeneration was observed in three 20,000 ppm and two 40,000 ppm males. Bone marrow hemorrhage and atrophy occurred in 40,000 ppm females. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were given 0, 630, 1,250, 2,500, 5,000, or 10,000 ppm pnitrobenzoic acid in feed for 13 weeks resulting in approximate daily doses of 40, 70, 160, 310, or 660 mg/kg to males and 40, 80, 170, 340, or 680 mg/kg to females. All rats survived until the end of the study. Mean body weight gains and final mean body weights were significantly less than those of the controls in 2,500, 5,000, and 10,000 ppm males and in 5,000 and 10,000 ppm females. There were no clinical findings related to organ-specific toxicity. Differences in spleen weights and hematology parameters characteristic of regenerative anemia were observed in males and females, primarily in groups given 10,000 ppm. The absolute and relative spleen weights were significantly increased in 10,000 ppm males and females and the relative spleen weights were significantly increased in 5,000 ppm males hts were significantly increased in 5,000 ppm males and females. Methemoglobin, Heinz bodies, and reticulocyte counts were increased and erythrocyte counts, hemoglobin, and hematocrit values were decreased in 10,000 ppm males and females. Congestion, pigmentation, and accumulation of macrophages in the spleen and pigmentation in the kidney occurred in 2,500, 5,000, and 10,000 ppm males. Congestion and pigmentation of the spleen occurred in 10,000 ppm females. A yellowish brown pigment (hemosiderin) in the spleen and kidney was associated with hemolytic anemia. Mild cytoplasmic hyaline droplet accumulation was present in renal tubule epithelial cells in 10,000 ppm males while karyomegaly was present in male and female rats exposed to 2,500, 5,000, and 10,000 ppm p-nitrobenzoic acid. A chemical-related testicular lesion, consisting of atrophy of the seminiferous tubules, occurred in 10,000 ppm males. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were given 0, 1,250, 5,000, 10,000, or 20,000 ppm pnitrobenzoic acid in feed for 13 weeks resulting in approximate daily doses of 170, 330, 670, 1,900, or 4,000 mg/kg body weight to males and 240, 460, 970, 2,500, or 4,900 mg/kg to females. All mice survived until the end of the study, except one 1,250 ppm female that was killed accidentally. Final mean body weights and mean body weight gains of all exposed males and of 5,000, 10,000, and 20,000 ppm females were significantly lower than those of the controls. No clinical findings or differences in organ weights or histopathology related to organ-specific toxicity were observed in exposed mice. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female rats were given 0, 1,250, 2,500, or 5,000 ppm p-nitrobenzoic acid in feed for 2 years. Ten males and 10 females from each exposure group were evaluated at 15 months. Survival, Body Weights, Feed Consumption, and Clinical Findings: Two-year survival rates of 1,250 and 2,500 ppm males were similar to that of the controls. Two-year survival of 5,000 ppm males was marginally greater than that of the controls and was attributed in part to a decrease in the severity of nephropathy and a decrease in the incidence of mononuclear cell leukemia. Survival of exposed females was similar to that of the controls. Mean body weights of 5,000 ppm males were 2% to 8% lower than those of the controls through week 80. Final mean body weights of exposed males were similar to that of the controls. Mean body weights of 5,000 ppm females were 2% to 9% lower than those of the controls during the first year of the study and were 10% to 16% lower during the second year of the study. Final mean body weights of exposed females were 97% (1,250 ppm), 92% (2;500 ppm), and 84% (5,000 ppm) that of the controls. Feed consumption by exposed males and females was similar to that by the controls. Dietary levels of 1,250, 2,500, or 5,000 ppm p-nitrobenzoic acid delivered approximately 50, 100, or 210 mg/kg body weight per day to males and 60, 125, or 250 mg/kg per day to females. There were no clinical findings attributable to organ-specific toxicity. Pathology Findings: There were increases in the incidences of clitoral gland adenoma and of clitoral gland adenoma or carcinoma (combined) (4/50, 14/49, 15/49, 15/50) in exposed females. The incidences of clitoral gland adenoma or carcinoma (combined) in the exposed groups (29% to 31%) exceeded the historical control mean incidence (11%) and range (2% to 21%) in female F344/N rats in recent 2-year NTP feed studies. The increased incidences of clitoral gland neoplasms were considered to be some evidence of carcinogenic activity in female rats exposed to p-nitrobenzoic acid. The incidences of hyperplasia of the clitoral gland in exposed females were marginally lower than that of the controls (10/50, 6/49, 6/ 49, 7/50). There was a chemical-related decrease in the severity of nephropathy in male rats. Male rat kidneys were examined using both single and step-section analyses, and the incidences of renal tubule neoplasms were not statistically greater than those of the controls. Mild hyaline droplet accumulation was observed in renal tubule epithelial cells in 10,000 ppm males in the 13-week study, but this effect was not severe enough to lead to a chemical-related neoplastic response in the 2-year study as has been observed with other chemicals. At the 15-month interim evaluation, hematologic parameters characteristic of a mild regenerative anemia and significant differences in spleen weights were noted in 5,000 ppm females. These differences included decreases in erythrocyte count, hemoglobin, and hematocrit, increases in spleen weights, and hemosiderin accumulation in splenic macrophages. At 2 years, significant decreases in the incidences of mononuclear cell leukemia were observed in 5,000 ppm males and 2,500 and 5,000 ppm females (males: 29/50, 35/50, 26/50, 2/50; females: 17/50, 11/50, 3/50, 0/50). While the mechanism for this decrease is unknown, decreases in the incidence of mononuclear cell leukemia have also been observed in 2year studies with other amine/nitro compounds. 2-YEAR STUDY IN MICE: Groups of 60 male and 60 female mice were given 0, 1,250, 2,500, or 5,000 ppm p-nitrobenzoic acid in feed for 2 years. Ten males and 10 females from each exposure group were evaluated at 15 months. Survival, Body Weights, Feed Consumption, and Clinical Findings: Two-year survival rates of exposed mice were similar to those of the controls. Mean body weights of 5,000 ppm males were 6% to 12% lower than those of the controls after week 17, and mean body weights of 5,000 ppm females were 12% to 24% lower than those of the controls after week 16. The final mean body weight of 5,000 ppm females was 19% less than that of the controls; final mean body weights of males were similar to that of the controls. Feed consumption by exposed mice was similar to that by the controls. Dietary levels of 1,250, 2,500, or 5,000 ppm p-nitrobenzoic acid delivered approximately 150, 300, or 675 mg/kg per day to males and 170, 365, or 905 mg/kg per day to females. There were no clinical findings of organ-specific toxicity. No chemical-related effects on hematology parameters were noted at the 15-month interim evaluation. Pathology Findings: There were no increases or decreases in neoplasms in male or female mice that were considered to be related to chemical administration. GENETIC TOXICOLOGY: p-Nitrobenzoic acid was mutagenic in Salmonella typhimurium strain TA100 with and without S9. No mutagenic activity was noted in strains TA98, TA1535, or TA1537, with or without S9. p-Nitrobenzoic acid induced sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells in the absence of S9; with S9, results of both tests were negative. In vivo, no increase in micronuclei was observed in peripheral blood erythrocytes of male or female mice administered p-nitrobenzoic acid in dosed feed for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of p-nitrobenzoic acid in male F344/N rats exposed to 1,250, 2,500, or 5,000 ppm. There was some evidence of carcinogenic activity of p-nitrobenzoic acid in female F344/N rats based on increases in the incidences of clitoral gland adenoma and of clitoral gland adenoma or carcinoma (combined). There was no evidence of carcinogenic activity of p-nitrobenzoic acid in male or female B6C3F1 mice exposed to 1,250, 2,500, or 5,000 ppm. There were chemical-related decreases in the incidences of mononuclear cell leukemia in exposed male and female rats. p-Nitrobenzoic acid caused mild hematologic toxicity in female rats. Synonyms: 4-Nitrobenzoic acid; nitrodracylic acid; p-nitrobenzenecarboxylic acid; p-carboxynitrobenzene
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PMID:NTP Toxicology and Carcinogenesis Studies of p-Nitrobenzoic Acid (CAS No. 62-23-7) in F344/N Rats and B6C3F1 Mice (Feed Studies). 1259 21

Polybrominated biphenyls are synthetic chemicals used as flame retardants. The technical product used in these studies, Firemaster FF-1(R)), is a mixture of brominated biphenyls. Firemaster FF-1(R)) is a known liver carcinogen in rats and mice and is one of three compounds chosen by the National Toxicology Program to investigate the potential value of perinatal exposures in assessing chemical carcinogenicity. Chronic toxicity and carcinogenicity studies of polybrominated biphenyls (Firemaster FF-1(R)) were conducted in F344/N rats and B6C3F1 mice of each sex. The studies were designed to determine: a) the effects of polybrominated biphenyls in rats and mice receiving adult ( F1) exposure only (a typical carcinogenicity study), b) the toxic and carcinogenic effects of polybrominated biphenyls in rats and mice receiving perinatal (F0) exposure only (dietary exposure of dams prior to breeding and throughout gestation and lactation), and c) the effects of combined perinatal and adult exposure to polybrominated biphenyls. STUDIES IN F344/N RATS: The exposure levels selected for F1 exposure, based on studies of polybrominated biphenyls in the literature, were 3, 10, and 30 ppm. In a preliminary study to determine the perinatal dietary concentrations for the 2-year study, female rats were administered 1 to 30 ppm polybrominated biphenyls in the feed beginning 60 days prior to breeding and continuing throughout gestation, lactation, and up to 4 weeks postweaning. The mean preweaning litter weight of the 30 ppm group was less than 80% of the mean litter weight of the control group at days 0, 4, and 12. At weaning, the mean weight of litters in this group was 80% of the control group mean. The final mean body weights (28 days after weaning) of males and females receiving 30 ppm were 13% to 19% lower than the final mean body weights of the controls. Therefore, dietary concentrations of 0, 1, 3, and 10 ppm were selected for the F0 exposure levels in the 2-year study. The eight F0 F1 exposure combinations selected for the 2-year study are shown in the following table (see page 6 of full technical report). Adult-Only Exposure The major organ affected by toxicity of polybrominated biphenyls was the liver. Rats evaluated at 9 months had decreased body weights, hepatomegaly, nonneoplastic histopathologic changes in the liver, mild anemia, increases in serum cholesterol concentrations, and decreases in serum triglyceride concentrations (males only). In rats receiving adult only exposure (F0 F1 concentrations of 0:10 or 0:30 ppm), there were no significant effects on survival. Mean body weights were significantly reduced in 0:10 and 0:30 ppm male rats and in 0:30 ppm female rats. Males and females exposed to 0:10 or 0:30 ppm had increased incidences of hepatocellular neoplasms (males: 0:0 ppm, 1/50; 0:10 ppm, 12/49; 0:30 ppm, 41/50; females: 0/50,12/50, 39/50). Increased incidences of the following nonneoplastic lesions were associated with the administration of polybrominated biphenyls: eosinophilic foci, cytoplasmic vacuolization, oval cell hyperplasia, and hypertrophy in the liver of males and females; acanthosis, inflammation, and ulceration of the forestomach in exposed males; and cystic endometrial hyperplasia of the uterus in 0:30 ppm females. Perinatal-Only Exposure For rats receiving only perinatal exposure (10:0 ppm), there were no changes in survival or body weights compared to the 0:0 ppm control groups. In female rats, there were no effects on neoplasm incidences, but perinatal exposure was associated with a marginally increased incidence of hepatocellular adenoma in male rats (0:0 ppm, 1/50; 10:0 ppm, 5/50). The incidences of nonneoplastic lesions in the liver were increased in exposed males (eosinophilic foci and cytoplasmic vacuolization) and females (eosinophilic foci). Combined Perinatal and Adult Exposure Combined perinatal and adult exposure resulted in marginally reduced survival compared to the 0:0 ppm control group for male rats in the 3:10, 10:10, and 10:30 ppm groups. No significant survival differences were obseant survival differences were observed in female rats. The final mean body weights of male and female rats receiving 3:10,10:10, or 10:30 ppm were lower than those of the 0:0 ppm controls. In male rats, there were no enhancing effects of combined perinatal and adult exposure on the incidence of hepatocellular neoplasms. However, perinatal exposure enhanced the development of liver neoplasms in female rats receiving 10 or 30 ppm adult exposure. A combined analysis of all male and female exposure groups also revealed increased incidences of mononuclear cell leukemia that were considered related to polybrominated biphenyls exposure. STUDIES IN B6C3F1 MICE: The exposure levels selected for the F1 exposure, based on studies of polybrominated biphenyls in the literature, were 3,10, and 30 ppm. In a preliminary study to determine the perinatal dietary concentrations for the 2-year study, female C57BL/6N mice were exposed to 1 to 30 ppm polybrominated biphenyls in the feed beginning 60 days before breeding to C3H/HeN males, continuing throughout gestation and lactation and up to 4 weeks postweaning. There were no clear chemical-related effects on survival or growth at any phase of the study; therefore, 0, 3,10, and 30 ppm dietary concentrations were selected for the F0 exposure levels in the 2-year study. The eight F0 F1 exposure combinations selected for the 2-year study are shown in the table below (see page 7 of full technical report). Adult-Only Exposure The major organ affected by toxicity of polybrominated biphenyls was the liver. Animals evaluated at 9 months had lower body weights than the controls, hepatomegaly, and histopathologic changes in the liver. In mice receiving adult-only exposure, no males or females in the 0:30 ppm group survived to the end of the study. Neither survival nor body weights were affected in the 0:10 ppm groups. Males and females receiving 0:10 or 0:30 ppm had markedly increased incidences of hepatocellular neoplasms (males: 0:0 ppm, 16/50; 0:10 ppm, 48/49; 0:30 ppm, 48/50; females: 5/50, 42/50, 47/48). Increased incidences of nonneoplastic liver lesions including cytomegaly (hypertrophy), fatty change (cytoplasmic vacuolization), bile duct hyperplasia, eosinophilic and clear cell foci, and necrosis of individual hepatocytes were related to treatment with polybrominated biphenyls. Increased incidences and severity of chronic nephropathy in the kidney and excessive hematopoiesis in the spleen of 0:30 ppm males and females were also considered to be related to exposure to polybrominated biphenyls. Perinatal-Only Exposure There were no survival or body weight differences in mice receiving only perinatal exposure (30:0 ppm). Perinatal exposure resulted in significantly increased incidences of hepatocellular neoplasms in males and females. The incidences of nonneoplastic lesions (cytomegaly, eosinophilic foci, clear cell foci) were increased in males and females. Combined Perinatal and Adult Exposure Combined perinatal and adult exposure resulted in markedly reduced survival for females in the 30:10 ppm group; no mice receiving 30:30 ppm survived to the end of the study. In those groups receiving adult exposure of 30 ppm, mean body weights were not affected. The incidence of hepatocellular neoplasms in male and female mice was significantly increased. At the 9-month interim evaluation the incidence of hepatocellular adenomas was significantly increased in males (0:30 ppm, 1/10; 30:30 ppm, 7/10). The incidence of hepatocellular adenomas in 30:30 ppm females was similar to that of 0:30 ppm females (0:30 ppm, 0/10; 30:30 ppm, 3/10). At the end of the study the incidence of hepatocellular adenomas in males was statistically increased (0:30 ppm, 42/50; 30:30 ppm, 48/50). The incidence of hepatocellular adenomas in 30:30 ppm females was statistically decreased compared to that of 0:30 ppm females (0:30 ppm, 46/48; 30:30 ppm, 41/47). It was not possible to assess the potential enhancing effect of combined perinatal and adult exposure on hepatocellular neoplasms because adult-only exposure resulted in such high (84% to 98%) liver neoplasm incidences. CONCLUSIONS: Adult-Only Exposure Under the conditions of these 2-year, adult-only, dietary exposure studies, there was clear evidence of carcinogenic activity for polybrominated biphenyls in male and female F344/N rats and male and female B6C3F1 mice based on increased incidences of hepatocellular neoplasms. Perinatal-Only Exposure Perinatal exposure alone (through dietary administration of 10:0 ppm polybrominated biphenyls to the dams) had no effect on the incidences of neoplasms in female F344/N rats, but in male F344/N rats, perinatal exposure was associated with a marginally increased incidence of hepatocellular adenomas that may have been related to chemical administration. In male and female B6C3F1 mice, perinatal exposure to 30:0 ppm polybrominated biphenyls resulted in significantly increased incidences of hepatocellular neoplasms. The incidences of a number of nonneoplastic lesions in the liver (cytomegaly, eosinophilic focus, and clear cell focus) were increased in male and female B6C3F1 mice. Combined Perinatal and Adult Exposure Combined perinatal and adult dietary exposure to polybrominated biphenyls confirmed findings of the adult-only exposures for the increased incidences of hepatocellular neoplasms in F344/N rats and B6C3F1 mice. In male F344/N rats, there were no enhancing effects of combined perinatal and adult exposure. However, perinatal exposure enhanced the susceptibility of female F344/N rats receiving adult exposure of 10 or 30 ppm to the induction of liver neoplasms. For male and female F344/N rats, a combined analysis of the incidences of leukemia in the adult-only, perinatal-only, and combined perinatal and adult exposure groups revealed an apparent association between increasing incidences of mononuclear cell leukemia and exposure to polybrominated biphenyls. In male and female B6C3F1 mice, it was not possible to adequately assess the enhancing effects of combined perinatal and adult exposure on hepatocellular neoplasms, because adult-only exposure to 10 or 30 ppm polybrominated biphenyls resulted in high incidences (84% to 98%) of liver neoplasms. However, with increased perinatal exposure, there were increases in the numbers of B6C3F1 mice with hepatocellular carcinomas and in the numbers of B6C3F1 mice with multiple hepatocellular adenomas, which suggests an enhancement of polybrominated biphenyls-related hepatocellular carcinogenicity associated with perinatal exposure. Synonyms: PBBs; polybrominated biphenyl mixture; hexabromobiphenyl (technical grade); brominated biphenyls; polybromobiphenyls
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PMID:NTP Toxicology and Carcinogenesis Studies of Polybrominated Biphenyls (CAS No. 67774-32-7)(Firemaster FF-1(R)) in F344/N Rats and B6C3F1 Mice (Feed Studies). 1263 61

3,3',4,4'-Tetrachloroazobenzene (TCAB) is not commercially manufactured but is formed as an unwanted by-product in the manufacture of 3,4-dichloroaniline and its herbicidal derivatives Propanil, Linuron, and Diuron. It occurs from the degradation of chloroanilide herbicides (acylanilides, phenylcarbamates, and phenylureas) in soil by peroxide-producing microorganisms; and is formed by the photolysis and biolysis of 3,4-dichloroaniline. Humans may be exposed to TCAB during the manufacture as well as the application of herbicides containing TCAB as a contaminant. TCAB was nominated by the United States Environmental Protection Agency for toxicity and carcinogenicity testing based on its structural and biological similarity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the potential for human exposure from the consumption of crops contaminated with 3,4-dichloroaniline-derived herbicides. Male and female Harlan Sprague-Dawley rats and B6C3F1 mice were administered TCAB (at least 97.8% pure) in corn oil:acetone (99:1) by gavage for 3 months (rats only) or 2 years. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female Harlan Sprague-Dawley rats were administered 0.1, 0.3, 1, 3, 10, 30, or 100 mg TCAB/kg body weight in corn oil:acetone (99:1) by gavage, 5 days a week, for 14 weeks; groups of 10 male and 10 female rats received the corn oil:acetone vehicle alone. Special study groups of 30 (dosed groups) or 6 (vehicle control group) female Harlan Sprague-Dawley rats were administered 0.1, 3, or 100 mg TCAB/kg body weight in corn oil:acetone (99:1) by gavage, 5 days a week, for 13 weeks; vehicle controls received the corn oil:acetone vehicle alone. All male and female rats survived to the end of the study. Terminal mean body weights of males were not significantly different from vehicle controls in any group. Terminal mean body weights of females administered 10 mg/kg or greater were significantly less than those of the vehicle controls. Mean body weight gains of all dosed groups of females were significantly less than those of the vehicle controls. The hematology results indicate that TCAB induced a microcytic normochromic responsive anemia in male Sprague-Dawley rats. Serum concentrations of total thyroxine (T4) and free T4 were significantly decreased in a dose-related manner in all dosed groups in both sexes compared to their respective vehicle controls; total triiodothyronine (T3) and thyroid stimulating hormone (TSH) concentrations were generally unaffected. There were no statistically significant differences in the BrdU labeling indices in the liver of males or females exposed to TCAB compared to their respective vehicle controls. Significant induction of hepatic 7-ethoxyresorufin-O-deethylase (EROD) and 7-pentoxyresorufin-O-deethylase activities was observed in all dosed groups of males and females. Significant induction of hepatic acetanilide-4-hydroxylase activity was observed in males exposed to 3 mg/kg or greater and all treated groups of females. EROD activities in the lung generally increased with increasing dose and were significantly greater in all treated groups of males and females compared to their respective vehicle controls. The highest concentrations of TCAB were observed in fat tissue with lower concentrations in the liver and lung. TCAB concentrations were significantly increased in a dose-dependent manner in all tissues from dosed groups relative to vehicle controls. At the end of the 3-month study, absolute and relative liver weights were significantly greater than those of the vehicle controls in all dosed groups of males and in females administered 10 mg/kg or greater. Absolute and relative lung weights were significantly greater in 100 mg/kg males and 3 mg/kg or greater females. Absolute and relative right kidney and spleen weights were generally significantly greater for all dosed groups of males. Absolute thymus weights of 10 mg/kg or greater males and absolute and relative thymus weights of 1 mg/kg or greater females were significantly less than those of the vehicle controls. In the liver, the incidences of midzonal to diffuse hepatocytic hypertrophy in males administered 1 mg/kg or greater and in females administered 10 mg/kg or greater were significantly greater than the vehicle control incidences. Hematopoietic cell proliferation occurred in most males administered 3 mg/kg or greater and most females administered 10 mg/kg or greater. The incidences of midzonal hepatocytic cytoplasmic fatty vacuolization were significantly increased in males administered 3 mg/kg or greater. In the lung, significantly increased incidences of bronchiolar metaplasia of the alveolar epithelium and interstitial mononuclear cell infiltration occurred in 10, 30, and 100 mg/kg males. The incidence of interstitial mononuclear cell infiltration was also significantly increased in 100 mg/kg females. Significantly increased incidences of hematopoietic cell proliferation of the spleen occurred in males administered 10 mg/kg or greater. The incidences of hemosiderin pigment of the spleen were significantly increased in 10 mg/kg or greater females. Atrophy in the thymus was significantly increased in all dosed groups of females, except the 0.1 mg/kg group, and in males administered 10 mg/kg or greater. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female Harlan Sprague-Dawley rats were administered 10, 30, or 100 mg TCAB/kg body weight in corn oil:acetone (99:1) by gavage, 5 days a week, for 2 years; groups of 50 male and 50 female rats received the corn oil:acetone vehicle alone. The survival of all dosed groups of males was significantly less than that of the vehicle controls. Mean body weights of 100 mg/kg males were less than those of the vehicle control group throughout the study. Mean body weights of 30 mg/kg males were 6% less than those of the vehicle control group after week 24, and those of 10 mg/kg males were 7% less than the vehicle control group after week 80. Mean body weights of 100 mg/kg females were less than those of the vehicle control group throughout the study, and those of 30 mg/kg females were 6% less than the vehicle control group after week 36. In the lung, the incidences of multiple cystic keratinizing epithelioma and single or multiple cystic keratinizing epithelioma (combined) in males and females were significantly increased in all dosed groups (except multiple epithelioma in 10 mg/kg females). Significantly increased incidences of pigmentation, alveolar epithelium squamous metaplasia (except 10 mg/kg females), and alveolar epithelium bronchiolar metaplasia occurred in all dosed groups of males and females. The incidences of histiocytic cellular infiltration in all dosed groups of males were significantly increased. In the liver, the incidences of cholangiocarcinoma (single or multiple) occurred in a positive trend in males and were significantly greater than that in the vehicle control group; the incidence in 100 mg/kg females was also increased. A significant dose-related increase in hepatic toxicity was observed in dosed rats and was characterized by increased incidences of numerous lesions including hepatocyte hypertrophy, centrilobular degeneration, hepatocellular necrosis, pigmentation, fatty change, bile duct hyperplasia, oval cell hyperplasia, nodular hyperplasia, hematopoietic cell proliferation, eosinophilic focus, mixed cell focus, multinucleated hepatocytes, bile duct cyst, toxic hepatopathy, and cholangiofibrosis. Significantly increased incidences of gingival squamous cell carcinoma within the oral mucosa occurred in 10 mg/kg males and 100 mg/kg males and females. The incidences of gingival squamous hyperplasia and cystic keratinizing hyperplasia in dosed groups of males and females were generally significantly increased. The incidences of follicular cell adenoma (single or multiple) of the thyroid gland in 30 and 100 mg/kg males were significantly greater than that in the vehicle control group. The incidences of follicular cell hypertrophy, follicular cell hyperplasia, and inflammation were significantly increased in 30 and 100 mg/kg males. Three incidences of single or multiple squamous cell papilloma of the forestomach occurred in 100 mg/kg females, and single incidences of squamous cell carcinoma of the forestomach occurred in 10 and 100 mg/kg females. Significantly increased incidences of epithelial hyperplasia occurred in all dosed groups of males and females. There were three incidences of malignant schwanomma in the thoracic cavity in 100 mg/kg males and a single incidence in 30 mg/kg males. In the adrenal cortex of 30 and 100 mg/kg females, there were slightly increased incidences of adenoma. In all dosed groups of males, the incidences of degeneration, cytoplasmic vacuolization, and hyperplasia of the zona fasciculata were significantly increased. Increased incidences and severities of necrosis occurred in 30 and 100 mg/kg males. Incidences of cytoplasmic vacuolation in 10 and 100 mg/kg females and hyperplasia of the zona fasciculata in 30 mg/kg females were significantly greater than those in the vehicle controls. Numerous nonneoplastic effects were seen in other organs including atrophy, acinar cytoplasmic vacuolization, and inflammation of the pancreas; blood vessel inflammation; lymphoid follicle atrophy and pigmentation of the spleen; pigmentation and atrophy of the mesenteric lymph node; germinal epithelial degeneration of the testes; and inflammation of the nose. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered 3, 10, or 30 mg TCAB/kg body weight in corn oil:acetone (99:1) by gavage, 5 days a week, for 2 years; groups of 50 male and 50 female rats received the corn oil:acetone vehicle alone. Survival of 10 and 30 mg/kg males and 30 mg/kg females was significantly less than that of vehicle controls. All 30 mg/kg males died before the end of the study. (ABSTRACT TRUNCATED)
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PMID:Toxicology and carcinogenesis studies of 3,3',4,4'-tetrachloroazobenzene (TCAB) (CAS No. 14047-09-7) in Harlan Sprague-Dawley rats and B6C3F1 mice (gavage studies). 2138 77

N,N-dimethyl-p-toluidine was nominated for toxicology and carcinogenesis studies by the National Cancer Institute based on the potential for human exposure through its use in dental materials and bone cements and the lack of toxicity and carcinogenicity data. Male and female F344/N rats and B6C3F1/N mice were administered N,N-dimethyl-p-toluidine (greater than 99% pure) in corn oil by gavage for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Escherichia coli, mouse peripheral blood, and mouse and rat liver. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were administered 0, 62.5, 125, 250, 500, or 1,000 mg N,N-dimethyl-p-toluidine/kg body weight in corn oil by gavage, 5 days per week for 14 weeks. Additional groups of 10 male and 10 female rats (clinical pathology study) were administered the same doses, 5 days per week for 25 days. On day 88, blood was collected from core study rats for hemoglobin and methemoglobin analyses only. All 1,000 mg/kg male and female rats and one 500 mg/kg male rat died by study day 3. Mean body weights of all surviving dosed groups of males and females were significantly less than those of the vehicle controls. Clinical findings associated with exposure to N,N-dimethyl-p-toluidine included cyanosis, abnormal breathing, and lethargy in groups administered 250 mg/kg or greater. Methemoglobinemia appeared to be the primary hematologic toxic response, and many other lesions could be explained as secondary to methemoglobin formation including Heinz body formation; a macrocytic, hypochromic, responsive anemia; and increased hematopoietic cell proliferation in the spleen and bone marrow. In general, hematologic changes were dose-related and occurred at both evaluated timepoints in all dosed groups. Anemia was evidenced by decreases in hematocrit values, hemoglobin concentrations, and erythrocyte counts; erythrocyte macrocytosis was characterized by increases in mean cell volume and mean cell hemoglobin values; erythrocyte hypochromia was evidenced by decreases in mean cell hemoglobin concentration values; and an erythropoietic response to the anemia was characterized by substantially increased reticulocyte and nucleated erythrocyte counts. Liver weights of all surviving dosed groups of males and females were significantly greater than those of the vehicle controls. Kidney weights of all surviving dosed groups of females were significantly greater than those of the vehicle controls. There were significant decreases in left cauda epididymis and left epididymis weights in 250 mg/kg males. There was a dose-related decrease in the number of cycling females, with only four females in the 250 mg/kg group having regular cycles and females in the 125 and 250 mg/kg groups spending a significantly higher proportion of time in extended diestrus compared to the vehicle control group. In the surviving groups of rats, there were significantly increased incidences of pigmentation in the liver of all dosed groups, hepatocyte hypertrophy in groups administered 125 mg/kg or greater, and hepatocyte necrosis in 62.5, 250, and 500 mg/kg females. In the olfactory epithelium of the nose, there were dose-related increases in the incidences and severities of degeneration in all dosed groups and significantly increased incidences of metaplasia in the 250 and 500 mg/kg groups. In the respiratory epithelium of the nose, there were significantly increased incidences of hyperplasia and squamous metaplasia in all of the groups administered 125 mg/kg or greater. The incidences of glandular hyperplasia of the nose were significantly increased in males and females administered 125, 250, or 500 mg/kg. In the spleen, there were significantly increased incidences of capsule fibrosis, congestion, mesothelial hypertrophy, and lymphoid follicle atrophy primarily in groups administered 125 mg/kg or greater. Hematopoietic cell proliferation and pigmentation were increased in severity in treated groups. In the kidney, there were significantly increased incidences of nephropathy (females), pigmentation (males and females), papillary necrosis (males and females), and mineralization (males). Other treatment-related lesions included inflammation of the forestomach in males, mesenteric lymph node atrophy in females, and bone marrow hyperplasia in males and females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were administered 0, 15, 30, 60, 125, or 250 mg N,N-dimethyl-p-toluidine/kg body weight in corn oil by gavage, 5 days per week for 14 weeks. All 250 mg/kg male and female mice (except for one male mouse) died before day 10, and three males and two females administered 125 mg/kg died before the end of the study. The final mean body weight of 125 mg/kg males and the mean body weight gains of 125 mg/kg males and females were significantly less than those of the vehicle controls. Clinical findings associated with administration of N,N-dimethyl-p-toluidine included abnormal breathing, thinness, lethargy, cyanosis, and ruffled fur in 125 and 250 mg/kg males and females. Methemoglobinemia appeared to be the primary hematologic toxic response; however there were less severe erythron changes compared to the 3-month study in rats. In females, no erythron changes were detected up to 125 mg/kg. In males, inconsistent and minor decreases in hematocrit values, hemoglobin concentrations, and erythrocyte counts, and increased reticulocyte counts occurred in groups administered 60 mg/kg or greater. Methemoglobin values were minimally increased in males and females administered 30 mg/kg or greater. Heinz bodies were slightly increased in 60 mg/kg females, 125 mg/kg males and females, and the one surviving 250 mg/kg male; Heinz body formation was considered secondary to methemoglobin formation. Liver weights of all dosed groups of mice were significantly greater than those of the vehicle controls. In the surviving groups of mice, there were significantly increased incidences of bronchiolar epithelium degeneration, bronchiolar epithelium regeneration, and peribronchiolar chronic active inflammation in the lung of 125 mg/kg groups, and histiocytic infiltrates of the alveoli in 125 mg/kg females. In the nose, there were significantly increased incidences of glandular hyperplasia and olfactory epithelium metaplasia in the 125 mg/kg groups and olfactory epithelium degeneration in 60 mg/kg females and 125 mg/kg males and females. In the thymus, the incidences of thymocyte necrosis in the 125 mg/kg groups were significantly increased. In the liver, the severities of cytoplasmic vacuolization of the hepatocytes were increased in dosed groups of males and females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 0, 6, 20, or 60 mg N,N-dimethyl-p-toluidine/kg body weight in corn oil by gavage, 5 days per week for 104 or 105 weeks. Additional groups of 10 male and 10 female rats (clinical pathology study) were administered the same doses for 86 days. Survival of 60 mg/kg males was significantly less than that of the vehicle controls. Mean body weights of 60 mg/kg males and females were more than 10% less than those of the vehicle controls after week 61 and week 33, respectively. Clinical findings included signs of pallor in 60 mg/kg females and hyperactivity and boxing behavior in 20 mg/kg females and 60 mg/kg males and females. The hematology findings at the 3-month timepoint were consistent with those in the 3-month study in rats which indicated that methemoglobinemia was the primary hematologic toxic response. In the 20 and 60 mg/kg groups, there were dose-related decreases in hematocrit values, hemoglobin concentrations, and erythrocyte counts. There were similar trends toward erythrocyte macrocytosis and hypochromia and increased erythropoiesis as seen in the 3-month study. While the magnitudes of the erythron decreases were not sufficient to classify the responses as anemias, the patterns of the erythron changes were identical to those in the 3-month study. In the liver of 60 mg/kg males and females, there were significantly increased incidences of hepatocellular carcinoma and hepatocellular adenoma or hepatocellular carcinoma (combined). Numerous nonneoplastic liver lesions occurred in dosed males and females primarily in the 20 and 60 mg/kg groups. In the nose, there were significantly increased incidences of transitional epithelium adenoma and transitional epithelium adenoma or carcinoma (combined) in 60 mg/kg males; transitional epithelium adenoma also occurred in female rats administered 6 or 60 mg/kg. In the nose, there were significantly increased incidences of nonneoplastic lesions in the olfactory, respiratory, and transitional epithelia of dosed rats. These lesions occurred with the greatest incidence and severity in the 60 mg/kg groups. The incidences of inflammation and nerve atrophy were significantly increased in males and females administered 60 mg/kg. There were increased incidences of follicular cell adenoma or carcinoma (combined) of the thyroid gland in all dosed groups of males, and an increased incidence of follicular cell adenoma in 20 mg/kg females. In the spleen, there were significantly increased incidences of hematopoietic cell proliferation in all dosed groups of males and females. The incidences of congestion and mesothelial hypertrophy of the capsule were significantly increased in 60 mg/kg males and all dosed groups of females. There were also significantly increased incidences of capsular fibrosis and atrophy of the lymphoid follicle in the 60 mg/kg groups. The incidences of pigmentation were significantly increased in all dosed groups of males and in 60 mg/kg females. In all dosed groups of female rats, there were significantly increased incidences of nephropathy. (ABSTRACT TRUNCATED)
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PMID:Toxicology and carcinogenesis studies of N,N-dimethyl-p-toluidine (CAS No. 99-97-8) in F344/N rats and B6C3F1/N mice (gavage studies). 2302 99


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