Selenium and Tellurium in Rats: Effect on Growth, Survival and Tumors

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Abstract
To evaluate the innate toxic effects of selenate, selenite and tellurite, 313 rats were given 2 ppm selenium or tellurium as these compounds in drinking water from the time of weaning until natural death, in a controlled environment. There were 105 controls. After 1 year, the doses of selenium were increased to 3 ppm. Selenite was extremely toxic, suppressing growth and causing high early mortality in males but less in females; the experiments were ended at 20 to 23 months. Selenate and tellurite were not toxic in terms of growth, survival and longevity. Selenium accumulated in five organs of control rats, although the diet contained only 0.05 µg/g wet weight; concentrations were more than doubled in selenium-fed animals, with kidney having the most. Fasting serum glucose levels were higher than controls in older selenium- and tellurium-fed males and in younger tellurium-fed females, without excess glycosuria. Fasting serum cholesterol levels were higher than the controls in selenium- and tellurium-fed rats of both sexes, and aortic lipids were considerably increased. In older animals, selenate was both tumorigenic and carcinogenic, whereas tellurite was not, there being 16.9% malignant tumors in the controls, 41.7% in the selenate and 18.2% in the tellurite groups.