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t-Butyl alcohol is widely used in the manufacture of perfumes and a variety of cosmetics. It is also used as a raw material in the production of isobutylene, which may be used to produce methyl tertiary butyl ether, a common gasoline additive, or to produce butyl elastomers used in the production of automobile tires. The National Cancer Institute nominated t-butyl alcohol to the NTP for study as a result of a review of chemicals found in drinking water. In addition to the high annual production and the potential for occupational exposure, there is also a potential for human exposure to t-butyl alcohol by the inhalation route from its use as an additive in unleaded gasoline. Therefore, toxicity studies of t-butyl alcohol were conducted in male and female F344/N rats and B6C3F1 mice by whole-body inhalation. Animals were evaluated for hematology, clinical chemistry, urinalysis, reproductive toxicity, and histopathology. The genetic toxicity of t-butyl alcohol was assessed by testing the ability of the chemical to induce mutations in various strains of Salmonella typhimurium and L5178Y mouse lymphoma cells or sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells, and by measuring the frequency of micronucleated erythrocytes in rat bone marrow and mouse peripheral blood. In the 18-day inhalation studies, groups of five male and five female rats and mice were exposed to t-butyl alcohol by inhalation at concentrations of 450, 900, 1,750, 3,500, and 7, 000 ppm for 6 hours per day, 5 days per week, for 12 exposure days. All rats and mice exposed to 7,000 ppm were killed moribund following a single 6-hour exposure. One 3,500 ppm male mouse died on day 3. Final mean body weights of 3,500 ppm male and female rats were significantly lower than those of the controls. Final mean body weights and body weight gains of all other exposed groups were similar to those of the controls. In animals exposed to 3.500 ppm, the thymus weights of male and female rats and female mice were less than those of the controls. The liver weights of male and female mice exposed to 3,500 ppm were greater than those of the controls. No grss or microscopic lesion were present in rats or mice. In the 13-week inhalation studies, groups of 10 male and 10 female rats and mice were exposed to t-butyl alcohol at concentrations of 0, 135, 270, 540, 1,080, and 2,100 ppm for 6 hours per day, 5 days per week, for 13 weeks. One 2,100 ppm and five 1,080 ppm male mice died before the end of the studies. The final mean body weight of 2,100 ppm female mice and the mean body weight gains of 1,080 and 2,100 ppm female mice were significantly lower than those of the controls. Clinical findings of toxicity in the 1,080 ppm male mice died during the studies included rough coats and emaciated appearance, hypoactivity, and prostration. Minimal decreases in hematocrit values, hemoglobin concentrations, and erythrocyte counts occurred in the 1,080 and 2,100 ppm male rats at week 13. Hemoglobin concentrations and/or hematocrit values were also minimally decreased in male rats in the lower exposure groups. At week 13, a minimal decrease in urine pH occurred in the 1,080 ppm female and 2,100 ppm male and female rats. Neutrophilia occurred in the 2,100 ppm male mice. Organ weight differences in exposed rats included increased absolute and relative kidney weights of 1,080 ppm males and 2,100 ppm males and females and increased relative liver weights of 1,080 and 2,100 ppm females. There were no treatment-related gross findings in male or female rats or mice; no microscopic lesion occurred in female rats or male or female mice that survived to the end of the study. In male rats, there was an exposure concentration-related increase in the severity of chronic nephropathy. Splenic lymphoid depletion was present in male mice that died during the studies; this lesion was presumed to be secondary to stress. t-butyl alcohol produced no adverse effects on reproductive parameters in male or female rats or mice. The results of all tests of t-butyl alcohol for induction of genetic damage in vitro and in vivo were negative. In vitro, t-butyl alcohol was negative in Salmonella typhimurium and mouse lymphoma cell mutation test, and it did not induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells. These in vitro studies were conducted with and without metabolic activation (S9). In vivo, no increase in the frequency of micronucleated erythrocytes was observed in peripheral blood samples from mice administered t-butyl alcohol in drinking water for 13 weeks. Also, induction or micronucleated erythrocytes was noted in bone marrow cells of rats administered t-butyl alcohol by intraperitoneal injection. In summary, inhalation exposure of rats and mice to t-butyl alcohol resulted in deaths following a single 7,000 ppm exposure and clinical findings of alcohol toxicity (hyper- and hypoactivity, ataxia) at concentrations of 900 ppm and greater in rats and 1,750 ppm and greater in mice. In 13-week studies at concentrations up to 2,100 ppm, only one death (that of a 2,100 ppm mouse) was attributed to chemical exposure. The most notable evidence of toxicity at the end of 13 weeks was limited to males and consisted of increased kidney weights, which correlated microscopically to increased severity of chronic nephropathy. Reproductive parameters in male and female rats and mice were unaffected after 13 weeks of exposure, and the results of all tests for genetic toxicity were negative.
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PMID:NTP technical report on toxicity studies of t-butyl alcohol (CAS No. 75-65-0). Administered by inhalation to F344/N rats and B6C3F1 mice. 1180 4

Methacrylonitrile is an aliphatic nitrile used extensively in the preparation of homo- and copolymers, elastomers, and plastics and as a chemical intermediate in the preparation of acids, amides, esters, and other nitriles. This aliphatic nitrile is also used as a replacement for acrylonitrile in the manufacture of an acrylonitrile/butadiene/styrene-like polymer. Methacrylonitrile was nominated for toxicity and carcinogenicity testing by the National Cancer Institute due to its high production volume and extensive use, the lack of chronic or carcinogenicity data, and its structural resemblance to the known rat carcinogen acrylonitrile. The current 13-week studies were conducted as part of an overall effort by the NTP to assess the toxicity and carcinogenicity of methacrylonitrile. During the 13-week studies, groups of 20 male and 20 female F344/N rats were administered 0, 7.5, 15, 30, 60, or 120 mg methacrylonitrile/kg body weight in deionized, purified water by gavage. Groups of 20 male and 20 female B6C3F1 mice were administered 0, 0.75, 1.5, 3, 6, or 12 mg/kg methacrylonitrile. Ten male and ten female rats and mice from each group were evaluated on day 32. The results of these studies clearly revealed that male rats are more sensitive than females to methacrylonitrile treatment. In the rat study, 19 males and one female administered 120 mg/kg and two males administered 60 mg/kg died during the first week of the study. Males in the 60 mg/kg group at the 32-day interim evaluation and at 13 weeks and females in the 120 mg/kg group at 13 weeks had significantly lower final mean body weights and body weight gains than did the vehicle controls; the surviving male in the 120 mg/kg group also weighed less than the controls at the 32-day interim evaluation. Clinical findings of toxicity were dose dependent and included lethargy, lacrimation, tremors, convulsions, ataxia, and abnormal breathing. There was hematologic evidence indicating that administration of methacrylonitrile induced minimal, normocytic, normochromic anemia. At the 32-day interim evaluation, a minimal dose-related anemia was evidenced by decreases in hematocrit values, hemoglobin concentrations, and erythrocyte counts in male and female rats. The anemia ameliorated by week 13. Administration of methacrylonitrile resulted in dose-related increases in serum thiocyanate and blood cyanide concentrations of male and female rats. These changes were expected and would be consistent with the in vivo metabolism of methacrylonitrile to cyanide. Blood cyanide concentrations were generally higher in males than in females, which may explain the higher sensitivity of males to the lethal effect of methacrylonitrile. There was also biochemical evidence of increased hepatocellular leakage and/or altered function in dosed male rats, suggesting that the liver may be a target organ for toxic effects of methacrylonitrile. Minimal, but significant, decreases in absolute right kidney and thymus weights (32-day interim evaluation) and increases in liver and stomach weights (week 13) occurred in male rats that received 60 mg/kg compared to the vehicle controls. In female rats, stomach weights of the 60 and 120 mg/kg groups were significantly greater and thymus weights of the 120 mg/kg group were significantly less than those of the controls on day 32 and at week 13; liver weights were also significantly greater in females in the 120 mg/kg group than in the vehicle controls on day 32. Male and female rats administered 60 mg/kg and females administered 120 mg/kg had significantly greater incidences of metaplasia of the nasal olfactory epithelium on day 32 and at the end of the study than did the vehicle controls; incidences of olfactory epithelial necrosis were also significantly greater in females in the 60 and 120 mg/kg groups than in the vehicle controls on day 32. Incidence and/or severity increased with increasing dose in females; however, the mortality in male rats administered 120 mg/kg made it difficult to assess the dose-response relationship in males. The no-observed-adverse-effect level for the nasal cavity of rats was 30 mg/kg. Female rats administered 60 or 120 mg/kg methacrylonitrile had significantly longer estrous cycles than did the vehicle controls. Females in the 60 mg/kg group spent more time in diestrus than the vehicle controls. One male and one female mouse in the 12 mg/kg groups died early. Methacrylonitrile administration caused no significant differences in final mean body weights or body weight gains. Clinical findings included lethargy, tremors, ataxia, convulsions, and abnormal breathing. At the 32-day interim evaluation, stomach weights of males administered 3 mg/kg or greater were significantly greater and thymus weights of males in the 12 mg/kg group were significantly less than those of the vehicle controls. At week 13, however, the stomach weights of only males in the 12 mg/kg group were increased relative to the vehicle controls. No treatment-related histopathologic lesions occurred in mice. Methacrylonitrile did not induce mutations in any of several strains of Salmonella typhimurium, with or without S9 activation, and did not induce sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster fed methacrylonitrile during the larval stage. Results of in vivo bone marrow micronucleus tests with methacrylonitrile in male rats and mice were also negative. In summary, gavage administration of methacrylonitrile to rats and mice resulted in dose-dependent lethargy, tremors, lacrimation, convulsions, and abnormal breathing. However, these effects were more pronounced in rats than mice; these differences may be attributed to the higher doses of methacrylonitrile administered to rats. Body weight gain and survival data of rats demonstrated that males are more sensitive to methacrylonitrile dosing than females. There is an apparent correlation between blood cyanide concentrations and survival rates, with males having greater cyanide concentrations and lower survival rates than female rats administered methacrylonitrile. Microscopically, the only target of methacrylonitrile toxicity was the olfactory epithelium of the nasal cavity. Necrotic and metaplastic effects were induced in male and female rats that received 60 or 120 mg/kg per day. No similar lesions were observed in mice administered methacrylonitrile. The no-observed-adverse-effect level for olfactory epithelial lesions in male and female rats administered methacrylonitrile for 13 weeks was 30 mg/kg per day. No clear chemical-related effects were observed in male or female mice administered methacrylonitrile for 13 weeks by gavage at doses up to 12 mg/kg per day.
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PMID:NTP technical report on the toxicity studies of methacrylonitrile (CAS No. 126-98-7). Administered by gavage to F344/N rats and B6C3F1 mice. 1180 6

Primidone is used alone or with other anticonvulsants in the control of grand mal, psychomotor, and focal epileptic seizures. It may control grand mal seizures refractory to other anticonvulsant therapy. Primidone was nominated by the National Cancer Institute for 2-year toxicology and carcinogenicity studies due to its human use as an anticonvulsant. Male and female F344/N rats and B6C3F1 mice received primidone (greater than 99% pure) in feed for 14 days, 14 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse bone marrow cells. 14-DAY STUDY IN RATS: Five male and five female rats were exposed to 0, 1,250, 2,500, 5,000, 10,000 or 20,000 ppm primidone (equivalent to average daily doses of approximately 120, 240, 500, 970, or 1,100 mg primidone/kg body weight to males and 120, 240, 500, or 900 mg/kg to females) in feed for 14 days. All 20,000 ppm females died before the end of the study as did one 10,000 ppm male and two 20,000 ppm males. The mean body weights of 10,000 ppm males and females and 20,000 ppm males were significantly less than those of the controls. Feed consumption by all exposed rats was generally similar to that by the controls. Males and females in the 10,000 and 20,000 ppm groups were observed to have eye discharge, ataxia, and abnormal posture and were thin and lethargic. 14-DAY STUDY IN MICE: Five male and five female mice were exposed to 0, 625, 1,250, 2,500, 5,000 or 10,000 ppm primidone (equivalent to average daily doses of approximately 100, 200, 400, or 800 mg/kg body weight to males and 100, 250, 500, or 900 mg/kg to females) in feed for 14 days. All mice in the 10,000 ppm groups and one male and one female mouse in the 5,000 ppm groups died on day 3 of the study. The mean body weights of mice in the 625, 1,250, 2,500, and 5,000 ppm groups were similar to those of the controls. Feed consumption by all exposed mice was generally similar to that by the controls. Males and females in the 10,000 ppm groups were observed to have abnormal posture, ataxia, and lethargy. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to 0, 300, 600, 1,300, 2,500, or 5,000 ppm primidone (equivalent to average daily doses of approximately 20, 40, 100, 200, or 400 mg/kg) in feed for 14 weeks. All rats survived to the end of the study. The mean body weights of male and female rats in the 2,500 and 5,000 ppm groups were significantly less than those of the controls. Feed consumption by all exposed rats was generally similar to that by the controls. A minimal to mild exposure-related thrombocytosis occurred on day 22 and at week 14 in all exposed groups of male rats and in females in the 1,300 ppm or greater groups. A minimal decrease in hemoglobin concentration occurred in 2,500 and 5,000 ppm male and female rats on day 22 and at week 14. The incidences of centrilobular hepatocyte hypertrophy in male rats exposed to 600 ppm or greater and in female rats exposed to 1,300 ppm or greater were significantly greater than those in the controls. The severity of chronic nephropathy in male rats exposed to 1,300 ppm or greater increased with increasing exposure concentration. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to 0, 300, 600, 1,300, 2,500, or 5,000 ppm primidone (equivalent to average daily doses of approximately 50, 100, 200, 400, or 1,000 mg/kg to males and 60, 120, 220, 440, or 1,100 mg/kg to females) in feed for 14 weeks. Three male and two female mice in the 5,000 ppm group died during week 1 of the study. The final mean body weights of all exposed groups were similar to those of the controls. Feed consumption by male mice in the 5,000 ppm group was slightly greater than that by the controls; this may have been due to feed spillage. Male and female mice in the 5,000 ppm groups were ataxic and lethargic. Compared to controls, the estrous cycle lengths of females exposed to 1,300, 2,500, or 5,000 ppm were significantly longer. The liver weights of male and female mice exposed to 600 po 600 ppm or greater were significantly greater than those of the controls. The incidences of centrilobular hepatocyte hypertrophy in all exposed males and in females exposed to 600 ppm or greater and the incidences of cytoplasmic alteration of the adrenal gland and hematopoietic cell proliferation of the spleen in 2,500 and 5,000 ppm males and in 5,000 ppm females were significantly greater than in the controls. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were exposed to 0, 600, 1,300, or 2,500 ppm primidone (equivalent to average daily doses of approximately 25, 50, or 100 mg/kg) in feed for 2 years. Survival, Body Weights, and Feed Consumption Survival of the 1,300 and 2,500 ppm males was sig nificantly less than that of the controls. The mean body weights of males and females in the 2,500 ppm groups were less than those of the controls, beginning at week 29 for males and week 17 for females; the mean body weights of 1,300 ppm males and females were less than those of the controls during the second year of the study. Feed consumption by all exposed groups of rats was generally similar to that by the controls. Pathology Findings Male rats exposed to primidone had increased inci dences of thyroid gland follicular cell neoplasms (adenoma and/or carcinoma). All exposed groups of male rats had follicular cell adenomas or carcinomas (combined) at incidences above the historical control range, with the highest incidence in the 1,300 ppm group. Hepatocyte cytoplasmic vacuolation and centrilobular hypertrophy were associated with primidone exposure in male and female rats. These changes were more severe in females than in males and the incidences in all exposed groups of females were significantly greater than those in the controls. Females in the 2,500 ppm group had an increased incidence of hepatocellular eosinophilic foci. In 2,500 ppm males, the incidence of renal tubule hyperplasia was greater than that in the controls in the standard evaluation. Additional hyperplasias were found in the extended evaluation, and the incidences in exposed groups of males were significantly greater than that in the controls. In the extended evaluation, the incidence of renal tubule adenoma in 2,500 ppm males was significantly increased. The incidence of adenoma or carcinoma (combined) in 2,500 ppm males in the combined standard and extended evaluations were marginally increased over those in the controls. Male rats had an exposure-related increase in the severity of chronic nephropathy, which probably accounted for the reduced survival in the 1,300 and 2,500 ppm groups. The incidences of kidney cysts were increased in 1,300 and 2,500 ppm males. Hyperparathyroidism, secondary to the loss of renal function, was present in many exposed male rats. The incidences of parathyroid gland hyperplasia in all groups of exposed males were significantly greater than that in the controls. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to dietary levels of 0, 300, 600, or 1,300 ppm primidone (equivalent to average daily doses of approximately 30, 65, or 150 mg/kg to males and 25, 50, or 100 mg/kg to females) in feed for 2 years. Survival, Body Weights, Feed Consumption, and Clinical Findings Survival of the 1,300 ppm males was significantly less than that of the controls. During the second year of the study, the mean body weights of 1,300 ppm male and female mice were less than those of the controls. The final mean body weights of 600 ppm males and females were less than those of the controls. Feed consumption by all exposed groups of mice was similar to that by the controls. During the latter part of the study, a treatment-related increase in the number of animals with swelling of the abdominal area was observed; necropsy revealed that the swelling was due to liver nodules/masses. Pathology Findings The liver was a target organ in both male and female mice. The incidences and multiplicities of hepatocellular neoplasms (hepatocellular adenoma, hepatocellular carcinoma, and hepatoblastoma) in all exposed groups of males and females (except hepatoblastoma in females) were significantly greater than those in the controls. The incidences of hepatocellular adenoma or carcinoma (combined) and hepatocellular adenoma, hepatocellular carcinoma, or hepatoblastoma (combined) in all exposed groups exceeded the historical control ranges in 2-year NTP studies. The incidences of centrilobular hepatocyte hypertrophy were increased in exposed groups of males and females, and the severities increased with increasing exposure concentration. The incidences of cytoplasmic vacuolization were increased in all exposed groups of females and in 300 ppm males. Incidences of eosinophilic focus in all exposed groups of females were significantly greater than those in the controls. Proliferative changes occurred in the thyroid gland in an exposure-related manner in male and female mice. Incidences of follicular cell hyperplasia were increased in all exposed groups of males and in 600 and 1,300 ppm females, but incidences of follicular cell adenomas were increased only in male mice. GENETIC TOXICOLOGY: Primidone was mutagenic in Salmonella typhimurium strain TA1535 in the absence of S9 activation only; no mutagenicity was detected in strain TA98, TA100, or TA1537, with or without S9. Primidone did not induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells, with or without S9. The single in vivo study with primidone, a mouse bone marrow micronucleus test, also gave negative results. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was equivocal evidence of carcinogenic activity of primidone in male F344/N rats based on a marginal increase in thyroid gland follicular cell neoplasms, primarily adenomas, and a marginal increase in renal tubule neoplasms. There was no evidence of carcinogenic activity of primidone in female F344/N rats exposed to 600, 1,300, or 2,500 ppm. There was clear evidence of carcinogenic activity of primidone in male B6C3F1 mice based on the increased incidences of hepatocellular neoplasms, and the increased incidence of thyroid gland follicular cell adenomas was also considered to be chemical related. There was clear evidence of carcinogenic activity of primidone in female B6C3F1 mice based on the increased incidences of hepatocellular neoplasms. Exposure of rats to primidone resulted in increased incidences of hepatocyte cytoplasmic vacuolization and centrilobular hypertrophy in males and females and eosinophilic foci in females. The increased severity of nephropathy and increased incidence of renal tubule hyperplasia in male rats were related to primidone exposure. Exposure of male mice to primidone resulted in hepatocyte centrilobular hypertrophy and thyroid gland follicular cell hyperplasia. Exposure of female mice to primidone resulted in hepatocyte centrilobular hypertrophy and cytoplasmic vacuolization, eosinophilic focus, and thyroid gland follicular cell hyperplasia. Synonyms: 5-Aethyl-5-phenyl-hexahydropyrimidin-4,6-dion; 2-deoxyphenobarbital; 2-desoxyphenobarbital; desoxyphenobarbitone; 5-ethyldihydro-5-phenyl-4,6 (1H,5H)-pyrimidinedione; 5-ethylhexahydro-4,6-dioxo-5-phenylphrimidine; 5-ethylhexahydro-5-phenylpyrimidine-4,6-dione; 5-ethyl-5-phenylhexahydropyrimidine-4,6-dione Trade names: Cyral; Hexadiona; Hexamidine; Lepimidin; Lepsiral; Majsolin; Midone; Milepsin; Misodine; Misolyne; Mizodin; Mizolin; Mylepsin; Mylepsinum; Mysedon; Mysoline; Prilepsin; Primacione; Primaclone; Primacone; Primakton; Primadon; Prysoline; Pyrimidone; ROE 101; Sertan
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PMID:NTP Toxicology and Carcinogenesis Studies of Primidone (CAS No. 125-33-7) in F344/N Rats and B6C3F1 Mice (Feed Studies). 1257 87

Tetrahydrofuran is used as a reaction medium for Grignard and metal hydride reactions; in the synthesis of butyrolactone, succinic acid, and 1,4-butanediol diacelate; in the fabrication of articles for packaging, transporting, and storing of foods; as a solvent for dyes and lacquers; and as a chemical intermediate in polymerization solvent for fat oils, unvulcanized rubber, resins, and plastics. Tetrahydrofuran is also an indirect food additive when it is in contact with the surface of articles intended for use in food processing. Tetrahydrofuran was nominated for study because of the potential for occupational exposure in humans. Male and female F344/N rats and B6C3F1 mice were exposed to tetrahydrofuran (approximately 99% pure) by inhalation for 13 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melanogaster, mouse bone marrow cells, and mouse peripheral blood cells erythrocites. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to 0 (chamber control), 66, 200, 600, 1,800, or 5,000 ppm tetrahydrofuran by inhalation, 6 hours per day, 5 days per week, for 14 weeks. All rats survived until the end of the study. Final mean body weights and mean body weight gains of exposed groups of male and female rats were similar to those of the chamber controls. Immediately after exposure, male and female rats in the 5,000 ppm groups exhibited ataxia. Hematologic and serum chemistry changes were minimal, with most values falling within physiologic ranges. Absolute and relative thymus and spleen weights of male and female rats exposed to 5,000 ppm were significantly less than those of the chamber controls. Absolute and relative liver weights of female rats exposed to 5,000 ppm were significantly greater than those of the chamber controls. Increased incidences of minimal to mild hyperplasia of the forestomach were observed in male and female rats exposed to 5,000 ppm. Minimal suppurative inflammation was associated with forestomach hyperplasia in two male rats and four female rats exposed to 5,000 ppm. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to 0, 66, 200, 600, 1,800, or 5,000 ppm tetrahydrofuran by inhalation, 6 hours per day, 5 days per week, for 14 weeks. Two male mice exposed to 5,000 ppm died during weeks 2 and 8 of the study; one male mouse from the 5,000 ppm group was killed in a moribund state during week 4. All female mice survived until the end of the study. The final mean body weights and mean body weight gains of all exposed groups of male mice were similar to those of the chamber controls. The final mean body weight and mean body weight gain of the 5,000 ppm female mice were significantly greater than those of the chamber controls. Male and female mice exposed to 1,800 or 5,000 ppm were observed in a state of narcosis (described by stupor) during exposure periods. Mice exposed to 1,800 ppm were fully awake and alert immediately after exposure; however, mice exposed to 5,000 ppm required up to 2 hours for recovery. Absolute and relative liver weights of male mice exposed to 600 ppm or greater and of female mice exposed to 1800 or 5,000 ppm were significantly greater than those of the chamber controls. Absolute and relative thymus weights of male mice exposed to 600, 1,800, or 5,000 ppm were significantly less than those of the chamber controls. The incidences of minimal to mild centrilobular cytomegaly of the liver in male and female mice exposed to 5,000 ppm were significantly greater than those in the chamber controls. The adrenal glands of all female mice exposed to 5,000 ppm had mild degeneration of the X-zone of the innermost cortex. Uterine atrophy was observed in all female mice exposed to 5,000 ppm. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to 0, 200, 600, or 1,800 ppm tetrahydrofuran by inhalation, 6 hours per day, 5 days per week, for 105 weeks. Survival, Body Weights, and Clinical Findings Survival and mean body weights of male and femand female rats exposed to tetrahydrofuran were similar to those of the chamber controls. Pathology Findings: The incidences of renal tubule epithelial adenoma or carcinoma (combined) in exposed males occurred with a positive trend, and the incidences in 600 and 1,800 ppm males exceeded the historical range for chamber controls in 2-year NTP inhalation studies. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to 0, 200, 600, or 1,800 ppm tetrahydrofuran by inhalation, 6 hours per day, 5 days per week, for 105 weeks. Survival, Body Weights, and Clinical Findings After week 36, the survival of male mice exposed to 1,800 ppm was significantly less than that of the chamber controls. Mean body weights of male and female mice exposed to tetrahydrofuran were similar to those of the chamber controls throughout the study. Male mice exposed to 1,800 ppm were observed to be in a state of narcosis during and up to 1 hour after the exposure periods. Pathology Findings: The incidences andmultiplicity of hepatocellular neoplasms were significantly greater in female mice exposed to 1,800 ppm than in the chamber controls. The incidence of nephropathy in 200 ppm male mice was significantly greater than that in the chamber control group. Male mice exposed to 1,800 ppm had significantly greater incidences of nonneoplastic lesions of the urogenital tract than did the chamber controls. The incidences of inflammation of the penis and urethra and necrosis of the urethra in 1,800 ppm males were slightly greater than those in the chamber controls; these may have been secondary effects of ascending urinary tract infection. GENETIC TOXICOLOGY: Tetrahydrofuran showed little evidence of mutagenic activity in a variety of in vitro and in vivo assays. It was not mutagenic in Salmonella typhimurium, and it did not induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells. These in vitro tests were conducted with and without exogenous metabolic activation from induced liver S9 enzymes. No increase in sex-linked recessive lethal mutations was detected in germ cells of male D. melanogaster exposed to tetrahydrofuran by feeding or injection. Results of in vivo assays for induction of chromosomal aberrations and sister chromatid exchanges in mouse bone marrow cells were negative. A micronucleus test in male and female mice exposed to tetrahydrofuran for 14 weeks showed no significant increases in the frequency of micronucleated erythrocytes in peripheral blood of female mice, but in male mice, analysis of micronucleated normochromatic erythrocyte levels revealed a small increase above baseline that was concluded to be equivocal. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of tetrahydrofuran in male F344/N rats based on increased incidences of renal tubule adenoma or carcinoma (combined). There was no evidence of carcinogenic activity of tetrahydrofuran in female F344/N rats exposed to 200, 600, or 1,800 ppm or male B6C3F1 mice exposed to 200, 600, or 1,800 ppm. There was clear evidence of carcinogenic activity of tetrahydrofuran in female B6C3F1 mice based on increased incidences of hepatocellular neoplasms. Synonyms: Butylene oxide; cyclotetramethylene oxide; diethylene oxide; 1,4-epoxybutane; furanidine; hydrofuran; oxacyclopentane; oxolane; tetramethylene oxide
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PMID:NTP Toxicology and Carcinogenesis Studies of Tetrahydrofuran (CAS No. 109-99-9) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). 1257 88

Oxazepam and related benzodiazepine drugs are used in the treatment of anxiety. All benzodiazepines currently in use share a number of effects, including sedation, hypnosis, decreased anxiety, muscle relaxation, amnesia, and anticonvulsant activity. Oxazepam and four other benzodiazepines (chlordiazepoxide, chlorazepate, diazepam, and flurazepam) were nominated for study by the Food and Drug Administration (FDA) and by the NIEHS based on their widespread use, use by pregnant women, and the lack of adequate rodent carcinogenicity studies. Oxazepam was evaluated in 14-week and 2-year studies by the NTP, and Technical Report No. 443 contains the results of the studies performed with the Swiss-Webster and B6C3F1 strains of mice. Studies with rats were not initiated at the same time as the mouse studies because adequate carcinogenicity studies of oxazepam with the Sprague-Dawley rat strain had been submitted to the FDA. Subsequently, because of the marked neoplastic responses found in the two mouse strains, the NTP initiated 2-year studies of oxazepam with the F344/N rat. Groups of male and female F344/N rats were exposed to oxazepam (greater than 99% pure) in feed for 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and cultured Chinese hamster ovary cells, and mouse peripheral blood samples were analyzed for the frequency of micronucleated normochromatic erythrocytes. 2-YEAR STUDY: Groups of 50 male and 50 female F344/N rats were fed diets containing 0, 625, 2,500, or 5,000 ppm oxazepam for up to 105 weeks. A stop-exposure group of 50 males and 50 females received 10,000 ppm oxazepam in feed for 26 weeks, after which animals received undosed feed for the remainder of the 2-year study. The continuous-exposure concentrations resulted in average daily doses of 25, 100, or 250 mg oxazepam/kg body weight to males and 25, 110, or 220 mg/kg to females. Stop- exposure males and females received an average daily dose of 630 mg/kg during the exposure period. Survival, Body Weights, and Clinical Findings: All 5,000 ppm continuous-exposure and 10,000 ppm stop-exposure males died before the end of the study. Survival of 2,500 ppm continuous-exposure males and females was significantly less than that of the controls. The mean body weight gains of 2,500 and 5,000 ppm males and females were less than those of the controls throughout the study. The mean body weights of 10,000 ppm stop-exposure males were generally less than those of the controls throughout the study; those of 10,000 ppm stop-exposure females were less than those of the controls during the exposure portion of the study but increased steadily after the cessation of dosing at week 27. Feed consumption by exposed groups was similar to that by the controls after week 1 of the study. Treatment-related eye/nasal discharge, hyperactivity when handled, and/or ataxia were observed in exposed male and female rats on or about day 2 of exposure but were no longer apparent after day 7. Plasma Oxazepam Determinations: Plasma oxazepam concentrations were measured at the end of the study. The concentrations ranged from approximately 0.5 (625 ppm males) to 2.8 &mgr;g/mL (5,000 ppm females). Pathology Findings: In the standard histopathologic evaluation, the incidence of renal tubule adenoma was slightly increased in male rats exposed to 2,500 ppm and was at the upper limit of the historical control range for this neoplasm in 2-year NTP feed studies. In an extended evaluation (step section) of the kidneys of male rats, the incidences of renal tubule adenoma occurred with a positive trend in exposed groups. In standard and step sections (combined), male rats exposed to 2,500 or 5,000 ppm showed a significant increase in the incidences of renal tubule adenoma and hyperplasia. In addition, the incidences of renal tubule adenoma and hyperplasia were significantly increased in the 10,000 ppm stop-exposure group. The incidences of nephropathy in continuously exposed female rats were significantly greater than in the controls, and the severity of nephropathy increased wised with increasing exposure concentration in males. The incidences of epithelial hyperplasia and chronic inflammation of the forestomach in males exposed to 2,500 and 5,000 ppm and of ulcers in 2,500 ppm males were significantly greater than in the controls. Incidences of mineralization of the glandular stomach in 5,000 ppm and 10,000 ppm (stop-exposure) males and of erosion of the duodenum in 5,000 ppm males were significantly greater than in the controls. Female rats exposed to 2,500 ppm had greater incidences of epithelial hyperplasia, chronic inflammation, and ulcers of the forestomach and of erosion in the glandular stomach. Centrilobular hepatocyte hypertrophy occurred more frequently in 2,500 and 5,000 ppm males and females than in the controls. GENETIC TOXICOLOGY: Oxazepam was not mutagenic in any of several strains of S. typhimurium, nor did it induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells. These in vitro tests were performed with and without S9 metabolic activation. Results from an in vivo mouse peripheral blood micronucleus test performed on B6C3F1 mice used in a 14-week study were also negative. CONCLUSIONS: In summary, under the conditions of these 2-year dosed-feed studies, there was equivocal evidence of carcinogenic activity in male F344/N rats, based on small increases in the incidences of renal tubule adenomas in exposed groups also exhibiting significantly enhanced nephropathy. There was no evidence of carcinogenic activity of oxazepam in female F344/N rats exposed to feed containing 625, 2,500, or 5,000 ppm for 2 years or 10,000 ppm for 6 months. Administration of oxazepam to rats resulted in nonneoplastic lesions in the forestomach, glandular stomach, and small intestine as well as centrilobular hypertrophy of hepatocytes in the liver. In addition, nephropathy was increased in incidence in female rats and was markedly increased in severity in male rats, resulting in early mortality at the higher exposure concentrations. Synonym: 7-Chloro-1,3-dihydro-3-hydroxy-5-phenyl-2H-1,4-benzodiazepin-2-one Trade Names: Tazepam, Wy-3498, Serax
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PMID:NTP Toxicology and Carcinogenesis Studies of Oxazepam (CAS No. 604-75-1) in F344/N Rats (Feed Studies). 1257 5

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

Coumarin is the basic structure of numerous naturally occurring compounds with important and diverse physiological activities. More than a thousand coumarin derivatives have been described, varying from simple coumarins containing alkyl and hydroxyl side chains to complex coumarins with benzoyl, furanoyl, pyranoyl, or alkylphosphorothionyl substituents. Coumarin and 3,4-dihydrocoumarin were nominated by the Food and Drug Administration and the National Cancer Institute for study because of the widespread use of coumarin in perfumes, cosmetics, and other products as a fragrance, continued interest in coumarin compounds as flavor-enhancing agents for foods, and the interest in structure-activity relationships of this important group of compounds. Coumarin is believed to be metabolized to a 3,4-epoxide intermediate, which may be responsible for its toxic effects, while 3,4-dihydrocoumarin, which lacks the 3,4-double bond, is not considered likely to form an epoxide intermediate. Toxicity and carcinogenicity studies were conducted by administering coumarin (97% pure) in corn oil by gavage to groups of male and female F344/N rats and B6C3F1 mice for 16 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melanogaster, and B6C3F1 mice. 16-DAY STUDY IN RATS: Groups of five male and five female rats received coumarin in corn oil by gavage at doses of 0, 25, 50, 100, 200, or 400 mg per kg body weight, 5 days a week for a total of 12 doses in a 16-day period. All female rats and four male rats receiving 400 mg/kg died. The mean body weight gains and final mean body weights of surviving dosed male and female rats were similar to those of the controls. There were no clinical signs of organ-specific toxicity, and there was no evidence of impaired blood coagulation from measurements of capillary clotting time or prothrombin and activated partial thromboplastin time. 16-DAY STUDY IN MICE: Groups of five male and five female mice received coumarin in corn oil by gavage at doses of 0, 40, 75, 150, 300, or 600 mg per kg body weight, 5 days a week for a total of 12 doses in a 16-day period. All mice receiving 600 mg/kg, two male mice receiving 300 mg/kg, and one male mouse receiving 75 mg/kg died. The mean body weight gains and final mean body weights of surviving dosed male and female mice were similar to those of the controls. Clinical findings of inactivity, excessive lacrimation, piloerection, bradypnea, ptosis, or ataxia were observed in some mice from the 300 and 600 mg/kg groups within the first several hours after dosing. Capillary clotting time and platelet counts of dosed mice were similar to those of controls. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats received coumarin in corn oil by gavage at doses of 0,19, 38, 75,150, or 300 mg per kg body weight. Three male and three female rats receiving 300 mg/kg died. The mean body weight gains and final mean body weights of male rats that received 150 and 300 mg/kg were significantly lower than those of the controls. There were no clinical signs related to specific organ toxicity. Male and female rats receiving coumarin exhibited dose-related decreases in mean erythrocyte volume and mean erythrocyte hemoglobin, and dose-related increases in erythrocyte counts. Serum levels of total bilirubin and one or more cytoplasmic enzymes including alanine aminotransferase, aspartate aminotransferase, ornithine carbamoyltransferase, and/or sorbitol dehydrogenase in males and females receiving 300 mg/kg were higher than those of controls. The absolute and relative liver weights of male and female rats that received 150 and 300 mg/kg were significantly greater than those of the controls. Centrilobular hepatocellular degeneration and necrosis, chronic active inflammation, and bile duct hyperplasia were observed in the liver of rats receiving 150 or 300 mg/kg. The high dose selected for the 2-year study was 100 mg/kg, which was just below the level at which mortality, lower final mean body weiody weights, and treatment-related liver lesions were observed in the 13-week study. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice received coumarin in corn oil by gavage at doses of 0, 19, 38, 75, 150, or 300 mg per kg body weight. Two male mice receiving 300 mg/kg died. The mean body weight gain and final mean body weight of surviving male mice that received 300 mg/kg were significantly lower than those of the controls. No clinical signs of toxicity were observed. Male and female mice receiving coumarin exhibited dose-related decreases in mean erythrocyte volume and mean erythrocyte hemoglobin. The absolute and relative liver weights of males and females that received 150 and 300 mg/kg were significantly greater than those of the controls. Centrilobular hepatocellular hypertrophy was observed in male and female mice receiving 300 mg/kg. The high dose selected for the 2-year study was 200 mg/kg, which was just below the level at which mortality and liver lesions were observed in the 13-week study. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female rats were administered coumarin in corn oil by gavage at doses of 0, 25, 50, or 100 mg per kg body weight. After 15 months, 10 animals from each group were evaluated. Survival, Body Weights, and Clinical Findings: None of the male rats receiving 100 mg/kg and only two males receiving 50 mg/kg survived until the end of the study (vehicle control, 28/50; 25 mg/kg, 9/50; 50 mg/kg, 2/51; 100 mg/kg, 0/50). Survival of dosed female rats was similar to that of the controls (29/50, 38/50, 36/50, 30/50). The reduced survival in dosed male rats was primarily attributed to chemical-related exacerbation of spontaneously occurring renal disease. Final mean body weights of female rats that received 100 mg/kg and all dosed groups of male rats were lower than those of the controls. There were no clinical signs of toxicity in rats, other than nonspecific signs relating to debilitation as a result of renal or other spontaneous disease. Hematology and Clinical Chemistry: At the 15-month interim evaluation, the values for one or more hematologic parameters including mean erythrocyte volume, mean erythrocyte hemoglobin in 50 and 100 mg/kg rats, and hematocrit or hemoglobin in 100 mg/kg rats were significantly lower than those of controls. Activated partial thromboplastin times were also significantly lower in 50 and 100 mg/kg males, while platelet counts were significantly higher. Activities of alanine aminotransferase, sorbitol dehydrogenase, or g-glutamyltransferase in 50 and 100 mg/kg male and 100 mg/kg female rats were significantly higher than those of the controls at the 15-month interim evaluation. Pathology Findings: The principal lesions associated with the administration of coumarin to rats for up to 2 years occurred in the liver, kidney, and forestomach. While the hepatic lesions were seen in all groups of males, they occurred only in the 50 and 100 mg/kg females. The lesions consisted of a spectrum of changes including hepatocellular necrosis, fibrosis, cytologic alteration, and increased severity of bile duct hyperplasia. The incidences of hepatocellular neoplasms were not increased in dosed rats. There was a chemical-related increase in the average severity of nephropathy in all groups of dosed male and female rats. There were corresponding increased incidences of parathyroid gland hyperplasia in all groups of dosed males, probably as a result of compromised renal function. In the standard evaluation of single kidney sections, a low incidence of renal adenomas was seen in all groups of males and in 100 mg/kg females (males: vehicle control, 1/49; 25 mg/kg, 2/50; 50 mg/kg, 2/51; 100 mg/kg, 1/50; females: 0/49, 0/50, 0/50, 2/49). An evaluation of step sections identified additional individuals with renal tubule focal hyperplasia (males: 2/49, 12/50, 10/51, 6/50; females: 1/49, 0/50, 4/50, 2/49) and adenoma (males: 0/49, 4/50, 5/51, 4/50; females: 0/49, 0/50, 1/50,1/49) in the dosed groups. The incidences of forestomach ulcers in all groups of dosed male rats and in 100 mg/kg female rats were significantly greater than those of the controls (males: 7/48, 24/50, 35/51, 34/50; females: 1/48, 1/49, 6/50, 9/48). STOP-EXPOSURE EVALUATION: A group of 40 male rats received 100 mg/kg coumarin in corn oil by gavage for 9 months, when 20 of the animals were necropsied and evaluated. The remainder of the male rats received only the corn oil vehicle during the 15-month recovery period. Similarly, a group of 30 male rats received 100 mg/kg coumarin in corn oil by gavage for 15 months, when 10 of the rats were necropsied and evaluated. The remaining 20 rats received only corn oil during the 9-month recovery period. A group of 20 vehicle control male rats were necropsied at 9 months, and another 10 vehicle control male rats were necropsied at 15 months. While chemical-related hepatic lesions were seen at both the 9- and 15-month interim evaluations, the incidences and severities of these lesions following the recovery period were generally similar to controls. Thus, the hepatic lesions produced by 9 or 15 months of exposure were reversible. In contrast to the liver lesions, the severity of nephropathy in male rats following the recovery period was significantly greater than that of males examined at the 9- and 15-month interim evaluations. This is not unexpected, since nephropathy is a progressive degenerative disease that naturally increases in severity with age. The incidence of renal tubule hyperplasia in the 15-month stop-exposure group (dosed for 15 months followed by the recovery period) and the incidence of renal tubule adenoma in the 9-month stop-exposure group were significantly greater than those of the control group. 2-YEAR STUDY IN MICE: Groups of 70 male and 70 female mice were administered coumarin in corn oil by gavage at doses of 0, 50, 100, or 200 mg per kg body weight for up to 2 years. After 15 months, 19 or 20 mice from each group were evaluated. Survival, Body Weights, and Clinical Findings: Survival of dosed male and female mice was similar to that of the controls (males: vehicle control, 43/50; 50 mg/kg, 47/50; 100 mg/kg, 42/50; 200 mg/kg, 37/51; females: 33/50, 40/50, 42/51, 28/51). The mean body weights of 200 mg/kg male and female mice were lower than those of controls throughout much of the study. There were no clinical findings related to chemical administration. Hematology and Clinical Chemistry: Mean erythrocyte volume, mean erythrocyte hemoglobin, and hematocrit of 200 mg/kg males and mean erythrocyte volume of 200 mg/kg females were significantly lower than those of the controls. Blood platelet counts of 200 mg/kg males and females were significantly higher than those of controls. There were no biologically significant differences in enzyme activities between dosed and control mice. Pathology Findings: The principal toxic lesions associated with the administration of coumarin to mice occurred in the liver. The incidences of centrilobular hypertrophy in 100 and 200 mg/kg males and 200 mg/kg females were significantly greater than those of controls. The incidences of syncytial alteration in all male dose groups and in 200 mg/kg females were also significantly greater than controls. The incidences of eosinophilic foci, a putative preneoplastic lesion, and of hepatocellular adenoma were significantly greater in the 50 and 100 mg/kg females. Hepatocellular carcinomas occurred with low incidences in the dosed females, but none occurred in the controls. The overall incidence of hepatocellular neoplasms (benign and malignant combined) in the 50 and 100 mg/kg females (control, 8/50; 50 mg/kg, 27/49; 100 mg/kg, 31/51; 200 mg/kg, 13/50) exceeds the range in historical controls (range 2%-34%; 129/898, 14.4%) from recent NTP studies. The reason for a lack of liver response in 200 mg/kg female mice is not known, but may be due in part to the decrease in body weight. While the incidences of eosinophilic foci were marginally greater in dosed male mice, the incidences of hepatocellular neoplasms were similar among the dosed and control groups. The incidences of alveolar/bronchiolar adenomas were significantly greater in 200 mg/kg male and female mice than in the controls. Further, the incidence of alveolar/bronchiolar carcinoma in 200 mg/kg females was also significantly greater than in controls. The overall incidence of pulmonary neoplasms (benign and malignant combined) in the 200 mg/kg groups (males: 14/50, 9/50,15/50, 25/51; females: 2/51, 5/49, 7/49, 27/51) exceeds the range in historical controls (males: range 6%-28%; 166/900, 18.4%; females: range 0%-14%; 58/899, 6.5%) from recent NTP studies. The incidence of squamous cell papilloma of the forestomach in 50 mg/kg males was greater than that of the controls (2/50, 8/50, 2/50, 0/51) and also exceeds the range of this neoplasm in control male mice from recent NTP studies (range 0%-14%; 27/902, 3.0%). The incidence of squamous cell papilloma of the forestomach in 50 mg/kg female mice was also slightly increased (1/52, 5/50, 2/51, 2/51); however, the incidence did not exceed the NTP historical range (27/901, 3%; range, 0%-10%). GENETIC TOXICOLOGY: Coumarin induced gene mutations in Salmonella typhimurium strain TA100 in the presence, but not in the absence, of exogenous metabolic activation (S9); no mutations were induced in strains TA98, TA1535, or TA1537, with or without S9. In Chinese hamster ovary cells, coumarin induced sister chromatid exchanges in the absence of S9, and chromosomal aberrations in the presence of S9. Coumarin did not induce sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster treated either as adults by feeding or injection, or as larvae by feeding. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood of male and female B6C3F1 mice administered coumarin by gavage for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year gavage studies there was some evidence of carcinogenic activity of coumarin in male F344/N rats based on increased incidences of renal tubule adenomas. There was equivocal evidence of carcinogenic activity of coumarin in female F344/N rats based on a marginally increased incidence of renal tubule adenomas. There was some evidence of carcinogenic activity of coumarin in male B6C3F1 mice based on the increased incidence of alveolar/bronchiolar adenomas. There was clear evidence of carcinogenic activity of coumarin in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar adenomas, alveolar/bronchiolar carcinomas, and hepatocellular adenomas. The marginally increased incidences of squamous cell papillomas of the forestomach in male and female mice receiving 50 mg/kg may have been related to coumarin administration. The administration of coumarin to rats was also associated with an increased severity of nephropathy in the kidney and of bile duct hyperplasia in the liver, increased incidences of ulcers of the forestomach, and necrosis, fibrosis, and cytologic alteration of the liver. Administration of coumarin to mice was also associated with centrilobular hypertrophy, syncytial alteration, and eosinophilic focus in the liver. Synonyms: 5,6-benzo-alpha-pyrone, 2H-1-benzopyran-2-one, 2H-benzolblpyran-2-one, 1,2-oxo-1,2-benzopyran, 1,2-benzopyrone, cis-o-coumarinic acid lactone, coumarinic anhydride, cumarin, o-hydroxycinnamic acid lactone, kumarin, [2-propenoic acid, 3-(-2-hydroxyphenyl)-delta-lactone], Rattex, tonka bean camphor
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PMID:NTP Toxicology and Carcinogenesis Studies of Coumarin (CAS No. 91-64-5) in F344/N Rats and B6C3F1 Mice (Gavage Studies). 1261 89

Benzyl acetate is used as a flavoring agent in foods, as a fragrance in soaps and perfumes, as a solvent for cellulose acetate and nitrate, and as a component of printing inks and varnish removers. The NTP previously studied the toxicology and carcinogenicity of this chemical in F344/N rats and B6C3F1 mice using the gavage route of administration and corn oil as a vehicle. Benzyl acetate increased the incidences of pancreatic acinar cell adenomas in male rats and the incidences of hepatocellular adenomas and forestomach neoplasms in male and female mice. Because of the confounding effect of corn oil on the incidences of pancreatic neoplasms and because of controversy over the use of the gavage route of administration, the NTP decided to restudy benzyl acetate using the dosed feed route of administration. In these repeat studies, male and female F344/N rats and B6C3F1 mice received benzyl acetate (at least 98% pure) in feed for 13 weeks and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium nunnery, cultured Chinese hamster ovary cells, LS178Y mouse lymphoma cells, Drosophila melanogaster, and mouse bone marrow and peripheral blood cells. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing 0, 3,130, 6,250,12,500, 25,000, or 50,000 ppm (0, 230, 460, 900,1,750, or 3,900 mg/kg body weight for males and 0, 240, 480, 930,1,870, or 4,500 mg/kg for females) benzyl acetate for 13 weeks. Nine male and nine female rats receiving 50,000 ppm benzyl acetate died or were killed moribund between weeks 2 and 8 of the study. The mean body weight gain and the final mean body weight of 25,000 ppm males were significantly lower (P</=0.01) than those of the control group. Feed consumption by exposed rats, except the 25,000 and S0,000 ppm males and 50,000 ppm females, was similar to that by the controls. The reduced feed consumption by 25,000 and 50,000 ppm males and 50,000 ppm females may have been due to toxicity or decreased palatability. Tremors and ataxia occurred only in the 50,000 ppm rats. These findings were first observed on day 15 in nine males and six females and continued until the end of the study. Cholesterol levels in 12,500 and 25,000 ppm females and triglyceride levels in 25,000 ppm females were lower than those in the controls. Chemical-related lesions occurred in the brain, kidney, tongue, and skeletal muscles of the thigh. Necrosis of the brain involving the cerebellum and/or hippocampus, degeneration and regeneration of the renal tubule epithelium, and degeneration and sarcolemma nuclear hyperplasia of the tongue and skeletal muscles occurred in most male and female 50,000 ppm rats. This effect was observed in the 1,000 mg/kg group in the previous gavage study (NTP, 1986). 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 0, 3, 130, 6,250, 12,500, 25,000, or 50,000 ppm (0, 425, 1,000, 2,000, 3,700, or 7,900 mg/kg body weight for males and 0, 650, 1,280, 2,980, 4,300, or 9,400 mg/kg for females) benzyl acetate. One 50,000 ppm male mouse died and one 50,000 ppm female mouse was killed moribund before the end of the study. Mean body weight gains and final mean body weights of all exposed male and female mice were significantly lower than those of the controls and the mean body weight gains decreased with increased exposure level. Feed consumption by 3,130 ppm males and all exposed females was lower than that by the controls. Tremors occurred only in females and were first observed on day 16 in three females receiving 50,000 ppm, day 94 in one female receiving 25,000 ppm, and day 93 in one female receiving 12,500 ppm. The tremors continued until the end of the study. Necrosis of the brain involving the hippocampus occurred in four 50,000 ppm mice, one male and three females. Hepatocellular necrosis also occurred in the male with brain lesions. On reexamination of the previous 13-week gavage study (NTP, 1986), a similar lesion was seen in the brain of one 1,000 mg/kg female mouse; none were seen in 1,000 mg/kg male mi male mice. The lesion was less severe than that described in the present dosed feed study. The highest dose used in the gavage study was 1,000 mg/kg compared to an estimated high dose of 7,200 mg/kg for the feed study. 2-YEAR STUDY IN RATS: The doses selected for the 2-year feed study of benzyl acetate in F344/N rats were based on lower survival, mean body weights, and feed consumption, and on increased incidences of histopathologic brain lesions in 50,000 ppm male and female rats in the 13-week study. Groups of 60 male and 60 female F344/N rats were fed diets containing 0, 3,000, 6,000, or 12,000 ppm benzyl acetate for 2 years. Survival, Body Weights, Feed and Compound Consumption, and Clinical Pathology: Survival of exposed rats was similar to that of the controls. The mean body weights of the 12,000 ppm males and exposed females were approximately 5&percnt; lower than those of the controls throughout most of the study. The feed consumption by 12,000 ppm males was slightly lower than that by the controls. Dietary levels of 3,000, 6,000, and 12,000 ppm benzyl acetate were estimated to result in average daily consumption levels of 130, 260, and 510 mg/kg body weight (males) and 145, 290, and 575 mg/kg (females). No biologically significant changes in hematology or clinical chemistry parameters were found that could be attributed to benzyl acetate administration. Pathology Findings: No compound-related increased incidences of neoplasms or nonneoplastic lesions occurred in male or female F344/N rats receiving benzyl acetate for as long as 2 years. 2-YEAR STUDY IN MICE: The doses selected for the 2-year feed study of benzyl acetate in B6C3F1 mice were based primarily on lower body weight gains and lower final mean body weights of exposed mice in the 13-week study. Groups of 60 male and 60 female B6C3F1 mice were fed diets containing 0, 330, 1,000, or 3,000 ppm benzyl acetate for 2 years. Survival, Body Weights, Feed and Compound Consumption, and Clinical Pathology: Survival of all exposed mice, except the 3,000 ppm females, was similar to that of the control groups. Survival of 3,000 ppm females was significantly higher than that of the control group. Throughout the 2-year study, the mean body weights of 1,000 and 3,000 ppm males and females were 2&percnt; to 14&percnt; lower than those of the control groups. Dietary levels of 330, 1,000, and 3,000 ppm benzyl acetate were estimated to result in average daily consumption levels of 35, 110, and 345 mg/kg (males) and 40, 130, and 375 mg/kg (females). No biologically significant changes in hematology or clinical chemistry parameters were observed in mice receiving 330,1,000, or 3,000 ppm benzyl acetate. Pathology Findings: No increase in neoplasm incidence in mice could be attributed to benzyl acetate administration in feed. This contrasts with the previous finding that administration of benzyl acetate in corn oil by gavage once daily 5 days a week for as long as 2 years was carcinogenic to mice, causing increased incidences of hepatocellular neoplasms and forestomach neoplasms. The contrast in results between the two studies may be due to differences in the dose levels used (highest dose: gavage, 1,000 mg/kg a day; feed, 360 mg/kg a day). Dose-related increased incidences or severities of nonneoplastic nasal lesions occurred in the most posterior portions of the nasal cavity in all exposed groups. The lesions occurred in the majority of the exposed mice and consisted of atrophy and degeneration, primarily of the olfactory epithelium, cystic hyperplasia of the nasal submucosal glands, pigmentation of the mucosal epithelium, and exudate accumulation. GENETIC TOXICOLOGY: Benzyl acetate was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537, with or without exogenous metabolic activation (S9). However, a positive response was observed for benzyl acetate, with and without S9, in the mouse lymphoma assay for induction of trifluorothymidine resistance in L5178Y cells. No significant increases in the frequencies of sister chromatid exchanges or chromosomal aberrations occurred in cultured Chinese hamster ovary cells treated with benzyl acetate in vitro, with or without S9, and no increases in either sister chromatid exchanges or chromosomal aberrations occurred in bone marrow cells of male mice treated in vivo by intraperitoneal injection. No increase in sex-linked recessive lethal germ cell mutations occurred in male Drosophila melanogaster administered benzyl acetate in feed or by injection. Tests of benzyl acetate for induction of micronucleated erythrocytes in bone marrow and peripheral blood of mice were also negative. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of benzyl acetate in male or female F344/N rats receiving 3,000, 6,000, or 12,000 ppm; however, rats may have tolerated higher doses. There was no evidence of carcinogenic activity of benzyl acetate in male or female B6C3F1 mice receiving 330, 1,000, or 3,000 ppm. Nasal lesions associated with benzyl acetate exposure in male and female mice included nasal mucosa atrophy and degeneration (primarily of the olfactory epithelium), cystic hyperplasia of the nasal submucosal gland, and luminal exudate and pigmentation of the nasal mucosal epithelium. In previous 2-year gavage studies (TR-250), benzyl acetate increased the incidence of acinar cell adenomas of the exocrine pancreas in male F344/N rats; the gavage vehicle may have been a contributing factor. There was no evidence of carcinogenic activity in female F344/N rats receiving 250 or 500 mg/kg a day. There was some evidence of carcinogenic activity in male and female B6C3F1 mice, indicated by the increased incidences of hepatocellular adenomas and squamous cell neoplasms of the forestomach. Synonyms: acetic acid benzyl ester, acetic acid phenyl methyl ester, (acetoxymethyl)benzene, acetoxytoluene, benzyl ethanoate, phenylmethyl acetate
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PMID:NTP Toxicology and Carcinogenesis Studies of Benzyl Acetate (CAS No. 140-11-4) in F344/N Rats and B6C3F1 Mice Feed Studies). 1261

Monochloroacetic acid, a colorless crystalline material, is used as a postemergence contact herbicide and as an intermediate in the synthesis of other organic compounds. Toxicology and carcinogenicity studies were conducted by administering monochloroacetic acid (99% pure) in deionized water by gavage to groups of F344/N rats and B6C3F1 mice of each sex once daily, 5 days per week for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, mouse lymphoma L5178Y cells, Chinese hamster ovary cells, and Drosophila melanogaster. 16-Day Studies: Groups of five rats of each sex received 0, 7.5, 15, 30, 60, or 120 mg monochloroacetic acid/kg body weight. Doses administered to mice were 0, 15, 30, 60, 120, or 240 mg/kg to groups of five males and 0, 30, 60, 120, 240, or 480 mg/kg to groups of five females. One of five male rats given 120 mg/kg died during the studies. Clear nasal discharge, lacrimation, or both, were observed in all groups of male and female rats receiving monochloroacetic acid. No compound-related gross lesions were observed in rats. All male mice given 240 mg/kg and all females given 240 or 480 mg/kg died during the studies. Hypoactivity, piloerection, ataxia, and lacrimation were observed in mice given 240 or 480 mg/kg. No compound-related gross lesions were observed in mice at necropsy. 13-Week Studies: Groups of 20 rats of each sex received 0, 30, 60, 90, 120, or 150 mg/kg monochloroacetic acid, and groups of 20 mice of each sex received doses of 0, 25, 50, 100, 150, or 200 mg/kg. Three to five animals in each dose group were killed at weeks 4 and 8 for the evaluation of hematology parameters. Compound-related deaths occurred in rats in the three highest dose groups (all males given 120 or 150 mg/kg, 9/10 males given 90 mg/kg, and all females given 90 to 150 mg/kg) and in mice given 200 mg/kg (all males and 2/10 females). Final mean body weights of surviving rats and mice receiving monochloroacetic acid were similar to those of controls. In rats, dose-related increases in blood urea nitrogen, alanine aminotransferase, and aspartate aminotransferase levels were observed, and relative liver and kidney weights were elevated. There were no compound-related changes in the various hematologic or clinical pathology parameters in mice. A dose-related increase in the incidence and severity of cardiomyopathy was observed in male and female rats receiving monochloroacetic acid, and hepatocellular cytoplasmic vacuolization was observed in the high-dose mice that died during the studies. 2-Year Studies: Based on the mortality and compound-related histopathologic lesions observed in the 13-week studies, doses selected for the 2-year studies of monochloroacetic acid were 0, 15, or 30 mg/kg, administered to groups of 70 rats of each sex, and 0, 50, or 100 mg/kg, administered to groups of 60 mice of each sex. Interim evaluations were conducted on 10 rats per dose group after 6 months of treatment with monochloroacetic acid and on seven rats per dose group after 15 months of treatment. Body Weight and Survival in the 2-Year Studies: Mean body weights of low- and high-dose female and low-dose male rats receiving monochloroacetic acid were within 10% of those of controls throughout the studies; however, after week 30, the mean body weights of high-dose male rats were 4% to 8% less than those of controls. In mice, the mean body weights of dosed males were similar to controls, but those of low- and high-dose females were 6% to 10% less than control values after week 52. Survival of high-dose male and dosed female rats and high-dose male mice was significantly lower than that of controls (male rats: control, 27/53; low-dose, 21/53; high-dose, 16/53; female rats: 37/53; 19/53; 26/53; male mice: 46/60; 39/60; 21/60; female mice: 42/60; 40/60; 44/60). Neoplasms and Nonneoplastic Lesions in the 2-Year Studies: There was no compound-related increase in the incidence of neoplasms or nonneoplastic lesions in rats given monochloroacetic acid for 2 years. The incidence of uterine stromal polypss. The incidence of uterine stromal polyps in low- and high-dose female rats was slightly higher than that in controls (2/60; 7/57; 10/60). However, the incidence in the controls was unusually low, and those in the dosed groups were well within the range for NTP historical controls (mean: 21&percnt;, range: 10&percnt;-38&percnt;). Further, because the only malignant stromal neoplasm occurred in a control animal, the polyps were not considered to be related to the administration of monochloroacetic acid. Similarly, there was no monochloroacetic acid-related increase in the incidence of neoplasms in male or female mice, and malignant lymphoma occurred with a significant negative trend in dosed female mice. Increases in the incidence of inflammation of the mucosa of the nasal passages, respiratory epithelial metaplasia of the olfactory epithelium of the nose, and focal squamous cell hyperplasia of the forestomach occurred in dosed male and female mice. Genetic Toxicology: Monochloroacetic acid was not mutagenic in Salmonella typhimurium strains TA100, TA1535, TA1537, or TA98, with or without exogenous metabolic activation (S9). It induced trifluorothymidine resistance in L5178Y cells in the absence of S9 and induced sister chromatid exchanges without S9 in Chinese hamster ovary cells. Monochloroacetic acid did not induce a significant increase in chromosomal aberrations in Chinese hamster ovary cells, with or without S9. Monochloroacetic acid administered in feed was negative for the induction of sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster; however, when it was administered by injection, the results were equivocal. Conclusions: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity for monochloroacetic acid in male or female F344/N rats given 15 or 30 mg/kg. There was no evidence of carcinogenic activity for monochloroacetic acid in male or female B6C3F1 mice given 50 or 100 mg/kg. Monochloroacetic acid administration was associated with inflammatory lesions of the nasal mucosa, metaplasia of the olfactory epithelium, and squamous cell hyperplasia of the forestomach in male and female mice. Synonyms: Chloroacetic acid, a-chloroacetic acid, chloroethanoic acid
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PMID:NTP Toxicology and Carcinogenesis Studies of Monochloroacetic Acid (CAS No. 79-11-8) in F344/N Rats and B6C3F1 Mice (Gavage Studies). 1263 63

NTP Toxicology and Carcinogenesis studies of a-methylbenzyl alcohol (greater than 99% pure), a cosmetic ingredient and food flavoring agent, were conducted by administering the chemical in corn oil by gavage to groups of F344/N rats and B6C3F1 mice of each sex for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, mouse lymphoma cells, and Chinese hamster ovary (CHO) cells. a-Methylbenzyl alcohol was nominated for study by the National Cancer Institute because of the potential for widespread human exposure. Sixteen-Day and Thirteen-Week Studies: The doses used in the 16-day studies for rats and mice ranged between 125 and 2,000 mg/kg. Six of 10 rats and all mice dosed at 2,000 mg/kg died. In addition, because 7/9 mice dosed at 1,000 mg/kg died, the doses selected for the 13-week studies for mice (47-750 mg/kg) were half those used for rats (93-1,500 mg/kg). In the 13-week studies, deaths of 1/10 male and 3/10 female rats dosed at 1,500 mg/kg were compound related; none of the mice died. Body weight gain was reduced in rats at 1,500 mg/kg; there were no significant histopathologic lesions in either rats or mice. The only compound-related effects were ataxia, labored breathing, and lethargy for up to 30 minutes after dosing in rats and mice given the two highest doses and increases in liver weight to body weight ratios for male rats given the three highest doses and for female rats at all doses. Based on the pattern of mortality and the effects on body weight gain in the short-term studies, doses of 375 and 750 mg/kg a-methylbenzyl alcohol were administered in corn oil by gavage, 5 days per week for 103 weeks, to groups of 50 rats and 50 mice of each sex. Two-Year Studies: Significant reduction in body weight gain commenced at weeks 20-30 in high dose male and female rats, and body weights were 20%-30% below those of vehicle controls at study termination. In the low dose groups, body weight reduction occurred only in male rats during the last 10 weeks of the study. After 80 weeks, 60% of the high dose rats and 80%-100% of the low dose and vehicle control rats were alive; thereafter, the number of deaths in the chemically exposed groups increased sharply so that, at the end of 2 years, final survival for vehicle control, low dose, and high dose rats was 35/50; 8/50; and 1/50 for males and 34/50, 25/50, and 11/50 for females. There were a large number of gavage accidents in these studies (1, 9, and 8 for male rats and 1, 4, and 14 for female rats), but these accidents did not contribute to the increase in mortality after week 80, as all but 4 of these occurred earlier. Mortality in the last quarter of the study was thought to be due to the effects of cumulative toxicity of a-methylbenzyl alcohol on a renal excretory system already compromised by aging. Renal nephropathy that commonly occurs during aging was found in all groups of rats, but the severity was greater in male rats dosed with a-methylbenzyl alcohol. In addition, a collection of nonneoplastic lesions (parathyroid hyperplasia, calcification of the heart and glandular stomach, and fibrous osteodystrophy of bone) was found in the dosed male rats; these lesions were probably secondary to mineral imbalance arising from renal dysfunction. Since survival was poor in low and high dose male and high dose female rats, the sensitivity of the study for detecting a carcinogenic effect in these groups was reduced. Despite this limitation, there were dose-related increases in the incidences of renal tubular cell adenomas or adenocarcinomas (combined) in male rats (vehicle control, 0/50; low dose, 2/50; high dose, 5/50). In addition, transitional cell papillomas of the urinary bladder were observed in one high dose male and two high dose female rats. In mice, a reduction in body weight gain was apparent in the high dose groups of males and females. Final survival rates in mice were similar among groups (male: 39/49; 40/50; 28/50; female: 41/50; 41/50; 38/50). No neoplastic or nonneoplastic lesions were attributed to a-methylbenzyl lesions were attributed to a-methylbenzyl alcohol administration in mice of either sex. Genetic Toxicology: a-Methylbenzyl alcohol was not mutagenic in S. typhimurium strains TA98, TA100, TA1535, or TA1537 when tested in the presence or absence of exogenous metabolic activation. a-Methylbenzyl alcohol produced a positive response without activation in the mouse L5178Y/TK+/- lymphoma assay for induction of trifluorothymidine resistance; it was not tested with activation. In cytogenetic tests with CHO cells, a-methylbenzyl alcohol induced chromosomal aberrations in the presence, but not the absence, of metabolic activation; no induction of sister chromatid exchanges was observed in CHO cells after exposure to a-methylbenzyl alcohol. Conclusions: Under the conditions of these 2-year gavage studies, there was some evidence of carcinogenic activityof a-methylbenzyl alcohol for male F344/N rats, as shown by increased incidences of renal tubular cell adenomas and adenomas or adenocarcinomas (combined). There was no evidence of carcinogenic activity for female F344/N rats administered 375 or 750 mg/kg. Renal toxicity characterized by severe nephropathy and related secondary lesions was observed in the dosed rats, and excessive mortality occurred during the last quarter of the studies. Poor survival reduced the sensitivity of the studies for detecting the presence of a carcinogenic response both in chemically exposed groups of male rats and in the high dose group of female rats. There was no evidence of carcinogenic activity of a-methylbenzyl alcohol for male or female B6C3F1 mice administered 375 or 750 mg/kg for 2 years. Synonyms: styrallyl alcohol; styralyl alcohol; a-methylbenzenemethanol; phenylmethylcarbinol; 1-phenethyl alcohol
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PMID:NTP Toxicology and Carcinogenesis Studies of a-Methylbenzyl Alcohol (CAS No. 98-85-1) in F344/N Rats and B6C3F1 Mice (Gavage Studies). 1269 35


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