tetrachlorvinphos and Body-Weight

A 28-day oral toxicity test of tetrachlorvinphos (TCV) was conducted in male and female Slc: Wistar rats by gavage at dose levels of 0, 10, 100 or 1000 mg/kg/day. The male and female rats showed dose-related inhibition of serum cholinesterase activity and erythrocyte acetylcholinesterase activity. At a dose of 1000 mg/kg, body weight gain was decreased in males, and there were 6 deaths in females. Adrenal gland, liver, kidney and thyroid gland weights were increased. The adrenal lesions were characterized by vacuolization and swelling of the cortex cells. The hepatic lesions consisted of vacuolization and necrosis of the hepatocytes. The renal lesions consisted of regeneration and necrosis of the tubular epithelial cells. These lesions were mostly observed at a dose of 1000 mg/kg. After a 14-day recovery period in the 1000 mg/kg group, the changes of cholinesterase, total cholesterol, gamma-glutamyltransferase, alkaline phosphatase, aspartate aminotransferase and blood urea nitrogen in serum were restored or showed a tendency toward recovery. However, the lesions in the kidney and adrenal remained. More than 14 days are therefore considered to be needed for recovery. At doses of more than 10 mg/kg, significant inhibition of the serum cholinesterase activity in both sexes, erythrocyte acetylcholinesterase activity in males, and lesions of the adrenal gland in females were observed. Target organs for TCV-treated rats were the adrenal, liver and kidney. It was concluded that the NOEL under this experimental condition is less than 10 mg/kg/day.

Topics: Administration, Oral; Animals; Body Weight; Eating; Female; Hematologic Tests; Lethal Dose 50; Male; Organ Size; Rats; Rats, Wistar; Tetrachlorvinphos; Time Factors

Groups of 80 male and 80 female B6C3F1 mice were fed diets containing 17.5, 64, 320, 1600, 8000, and 16000 ppm tetrachlorvinphos (TCVP) for up to 103 weeks. Another group of 80 male and 80 female mice were fed TCVP (16000 ppm) that was used in a previous bioassay. One hundred-sixty male and 160 female mice served as the control group. Ten treated and 20 control mice/sex/group were killed at 6, 12, and 18 months. It was estimated that the study maximum-tolerated dose was exceeded by three- and sixfold in the 8000- and 16000-ppm dose groups, respectively. Consequently, these exposures produced excessive cytotoxicity and regenerative changes in the liver and kidneys which were associated with sex-hormonal imbalance and metabolic overload in liver. A significant decrease (15-40%) in body weight was observed in mice fed 8000 and 16000 ppm TCVP. These treated mice did not gain weight during the study. Reduced food consumption and caloric intake throughout the study were probably responsible for the increased survival and the decreased incidence of spontaneous neoplasia in mice fed 8000 and 16000 ppm TCVP. Classification of pathologic lesions observed in these high-dose groups differed among study and consulting pathologists. The consultant and Shell pathologists concluded that the liver and kidney changes were causally related to excessive toxicity which was manifest primarily by hepatocellular hyperplasia and renal tubular adenoma. Study pathologist in accordance with his classification found statistically significant increases in hepatocellular carcinoma, hepatocellular adenoma or carcinoma, and renal tubular carcinoma in male mice fed 16000 ppm TCVP. The incidence of hepatic neoplasms as evaluated by the study pathologist in female mice fed 8000 and 16000 ppm TCVP although statistically significant was of questionable biologic significance when compared with historical female controls. The only statistically significant finding observed by the consulting pathologist was an increased incidence of renal tubular adenoma and renal tubular adenoma or carcinoma in male mice fed 16000 ppm TCVP. Use of results from these high-dose groups is contraindicated due to the many compromising factors affecting mice fed 8000 and 16000 ppm TCVP. TCVP was found not to be oncogenic in B6C3F1 mice at dose levels not exceeding the maximum tolerated dose.

Topics: Animals; Body Weight; Female; Male; Mice; Mice, Inbred Strains; Neoplasms, Experimental; Organ Size; Tetrachlorvinphos; Time Factors