The effects of different levels of selenium administered to rats in drinking water on distribution and glutathione peroxidase.

Studies were conducted in an attempt to define a biochemical index of selenium toxicity rather than weight loss, liver disease and death. Rats, maintained on selenium deficient diets, received in drinking water various levels of selenium as Na2SeO3(0.1, 1.0, 1.5, 2.0 ppm). Changes in selenium dependent glutathione peroxidase (GSH-Px) activities and specific activities (nCi75Se/ug Se) were determined in liver, kidney and plasma at baseline and two and ten weeks after repletion. In intial selenium deficient rats, GSH-Px activities were markedly depressed and specific activities elevated as compared to 0.1 ppm controls. After two weeks, liver and plasma GSH-Px activiities increased, and plasma, liver and kidney specific activities decreased in a concentration dependent manner. In kidney, there were no differences in enzyme activity at either two or ten weeks. At ten weeks, liver GSH-Px activities continued to increase in the 1.0 ppm group, but were depressed at both the 1.5 and 2.0 ppm levels. Specific activities were also depressed in liver and excretion was not increased at these levels. This suggests a biochemical toxicity in liver at levels above 1.0 ppm after ten weeks, prior to the onset of gross pathological changes.