Response of Glutathione Peroxidase to Dietary Selenium in Rats

Abstract

The effect of dietary selenomethionine on the enzyme activities of the glutathione (GSH) peroxidase system in rat tissues was studied. The activity of GSH peroxidase decreased to varying degrees in tissues from animals fed a basal low selenium Torula yeast diet for 17 days. The relative decrease was plasma > kidney, heart, liver and lung > erythrocytes > testes. The activity of GSH peroxidase in all tissues except testes was significantly and linearly increased above that of the nonsupplemented controls when selenium-depleted animals were subsequently fed the same diet supplemented with 2 ppm selenium for 11 days. The relative increase was plasma > kidney > heart, erythrocytes, lung, and liver > testes. Dietary selenium did not significantly alter the activities of GSH reductase and glucose-6-phosphate (G-6-P) dehydrogenase. Intraperitoneal administration of actinomycin D or puromycin neither effectively suppressed the increase of GSH peroxidase activity nor inhibited the activities of GSH reductase and G-6-P dehydrogenase; however, it is possible that insufficient dosages were administered. In vitro studies with tissue soluble fractions and plasma from rats fed diets with low or high selenium levels suggest that selenium is not an exchangeable or a dialyzable cofactor for GSH peroxidase. These studies provide further evidence of the essentiality of selenium for the activity of GSH peroxidase.