Effects of various dietary selenium intakes on the levels of blood glutathione-peroxidase and selenium in long-term fed rats.

Female Sprague-Dawley rats were fed a torula diet or wheat diets containing 4 levels of Se partially supplemented (24-402 ppb) for 120 days. Selenium content and glutathione-peroxidase (GSH-Px) activity in plasma and erythrocytes were measured every 20 days. In rats fed torula diet or basal wheat diet, plasma Se (P-Se) increased for up to 60 days, then remained constant, while erythrocytes Se (E-Se) and E-GSH-Px decreased in basal-diet rats during the first 40-60 days, then increased. In rats fed supplemented diets, P-Se and P-GSH-Px increased more rapidly than E-Se and E-GSH-Px, plateauing at 60-80 days. The best correlation was found between P-GSH-Px and dietary Se indicating that this index is the most sensitive for evaluating changes resulting from different Se intakes. In addition, correlations became more significant with time. The results from rats fed a low Se diet suggest the existence of regulatory mechanisms working in different ways and at different times in plasma and erythrocytes.