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Barium Chloride dihydrate (BaCl2.2H2O) was given for 92 days to B6C3F1 mice and Fischer 344/N rats in their drinking water at levels of 0, 125, 500, 1000, 2000, and 4000 ppm. The no-effect level for this study was 2000 ppm BaCl2.2H2O in the drinking water. At 4000 ppm, daily consumption for mice was 436 to 562 mg/kg barium, up to four times more chemical than rats. Mortality ranged from 60 to 70% in mice and from 10 to 30% in rats in the 4000 ppm groups. Deaths in mice were associated with a treatment-related renal toxicity. Renal lesions in rats were much less severe than in mice and did not contribute to the treatment-related deaths seen in the high dose group. Body weights of both species and sexes in the 4000 ppm groups were lower than controls at 92 days. Male and female rats in treated groups exhibited higher serum phosphorus than controls. Serum sodium, potassium, and calcium levels in rats were unchanged by barium treatment, as were hematological values. In both species at 4000 ppm, motor activity, grip strength, and thermal sensitivity were marginally affected. These effects were probably secondary changes resulting from BaCl2 toxicity observed at this dose level. In a mating trial, no anatomical effects on offspring of rats or mice were seen. Rats receiving 4000 ppm exhibited marginal reductions in pup weights. No effects were seen on reproductive indices.

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Phenolphthalein is a cathartic agent that is widely used in over-the-counter laxatives. Thirteen-week toxicity studies of phenolphthalein were performed using F344/N rats and B6C3F1 mice. Rats and mice were fed ad libitum with a NIH 07 diet containing 0; 3000; 6000; 12,000; 25,000; or 50,000 ppm phenolphthalein. On a milligram per kilogram body weight basis, rats and mice fed 50,000 ppm phenolphthalein ingested more drug than would be expected during human laxative abuse. Phenolphthalein produced little evidence of toxicity in rats. There was slightly lower weight gain among the 25,000 and 50,000 ppm groups. Treated rats showed elevated relative kidney weights (males only) and elevated absolute and relative liver weights at 12,000-50,000 ppm phenolphthalein. Rat serum bile acids were depressed early (Days 5 and 6) by phenolphthalein treatment. Several treatment-related toxic effects, however, were identified in mice who received more phenolphthalein per unit body weight than rats. Although there were no effects on body weight gain, elevated liver weights were noted in female mice receiving 6000-50,000 ppm phenolphthalein. The primary treatment-related findings that occurred during the mouse studies involved the reproductive and hematopoietic systems. Reproductive changes including depressed testis and right epididymal weights and sperm density, an elevated production of abnormal sperm, and morphologic alterations in seminiferous tubules occurred at all levels of exposure (3000-50,000 ppm). Hematopoietic changes included bone marrow hypoplasia (12,000-50,000 ppm), increased splenic hematopoiesis (males only; 25,000 and 50,000 ppm), and an elevated incidence of micronucleated erythrocytes (6000-50,000 ppm).

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Two-year toxicity and carcinogenicity studies of oxytetracycline hydrochloride and tetracycline hydrochloride, two structurally similar and widely used antibiotics, were performed in F344/N rats and B6C3F1 mice. Rats and mice were continuously exposed via their diet to the following levels of antibiotic: oxytetracycline HCl--rats 0, 25,000, or 50,000 ppm; mice 0,6,300, or 12,500 ppm; tetracycline HCl--rats and mice 0, 12,500, or 25,000 ppm. On a milligram per kilogram of body weight basis these exposures represent doses that are 20 to 140 times daily human therapeutic doses. Dose-related increased survival was noted among oxytetracycline-treated male rats and tetracycline-treated female rats and male mice, while treatment-related reduced body weight gain occurred in oxytetracycline- and tetracycline-treated mice. Microscopic changes included fatty metamorphosis and focal cellular change in livers of oxytetracycline-treated male rats and basophilic cytoplasmic and clear cell change in livers of tetracycline-treated male rats. The only neoplastic changes were a marginally increased trend in pheochromocytoma of the adrenal medulla (equivocal evidence only) among oxytetracycline-exposed male rats (12/50 controls, 19/50 low dose, 24/50 high dose) and an increased incidence of pituitary adenoma or adenocarcinoma among high-dose oxytetracycline-treated female rats (20/50 controls, 32/50 high dose). Although oxytetracycline and tetracycline appeared to increase the incidence of pituitary hyperplasia in high-dose male and female rats, respectively, the total incidence of proliferative changes (hyperplasia, adenoma, and adenocarcinoma) was not affected by antibiotic exposure. The results from these studies therefore support the notion that neither antibiotic is carcinogenic in rodents. There were several negative trends suggesting possible protective effects by both these tetracycline analogs against certain spontaneous neoplastic and non-neoplastic changes.

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Two- and thirteen-week toxicity studies were conducted using male and female F344/N rats and B6C3F1 mice. Animals were exposed to the following concentrations of acetone in their drinking water: two-week studies 0; 5000; 10,000; 20,000; 50,000; or 100,000 ppm acetone. Thirteen-week rat and female mouse studies 0; 2500; 5000; 10,000; 20,000; or 50,000 ppm acetone. Thirteen week male mice were exposed to 0; 1250; 2500; 5000; 10,000; or 20,000 ppm acetone. Depressed body weight gain was restricted to the 50,000 and 100,000 ppm exposure groups. Male and female mice exposed respectively to 20,000 or 50,000 ppm acetone for 2 weeks developed hepatocellular hypertrophy. This change was not apparent after 13 weeks of exposure although relative and absolute liver weight was increased in high dose female mice. Bone marrow hypoplasia was observed in 5/5 high dose (100,000 ppm) male rats during the 2-week studies. Treatment of male rats for 13 weeks resulted in a variety of mild and subtle hematological changes that often occurred at relatively low levels of exposure (5000 ppm) and resembled those seen during the clinical condition of megaloblastic anemia. Changes characteristic of hypogonadism (depressed sperm motility and cauda epididymal and epididymal weight and elevated incidence of abnormal sperm) were observed in male rats receiving 50,000 ppm acetone for 13 weeks. The incidence and severity of a kidney lesion that is morphologically similar to the spontaneously occurring nephropathy among aging F-344 rats were increased at 20,000 and 50,000 ppm acetone, respectively, in 13-week male rats. In summary, the effects of acetone were either subtle in nature or occurred during very high levels of exposure confirming acetone's low level of toxicity. The daily levels of acetone exposure were often several-fold greater than possibly encountered by humans during the accidental consumption of contaminated groundwater (250 ppm; 5 mg/day) and frequently exceeded maximum levels reported following acute toxic exposures (2,500 mg/kg).

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The effects of lead acetate and aging on temporally-spaced responding (differential reinforcement of low rate or DRL-20 seconds) were studied. Three groups of animals were considered along with their respective controls. Neonate-treated Long-Evans rats were orally intubated with 200 mg/kg lead acetate from the third to 30th day after birth. Some of these animals were tested at 3 months (adult group) and some at 21 months (geriatric group) of age. A continuously treated group was exposed to 250 ppm lead in utero and throughout their life after birth and was treated at 8 months of age. Lead-treated animals exhibited a more variable response to d-amphetamine and a more pronounced number of IRTs in the first class interval. Aging shifted the pentobarbital dose-response curve to the left in both control and lead-treated animals and flattened interresponse time (IRT) distributions.

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