Incorporation of Selenium into Liver Glutathione Peroxidase in the Se-Adequate and Se-Deficient Rat 1

Abstract

Abstract

The biosynthesis of glutathione peroxidase was studied by measuring the rate of selenium (Se) incorporation into liver glutathione peroxidase in Se-adequate (0.2 ppm dietary Se as Na₂SeO₃) and Se-deficient rats (<0.02 ppm dietary Se). Rats were injected iv with [⁷⁵Se]selenite (1.29 μg Se/100 g rat) and sacrificed 0.5, 1, 3, 6, 12, 24, or 72 hr post-injection. Sephadex G-150 chromatography of liver supernatant was used to determine the level of ⁷⁵Se incorporation into glutathione peroxidase. Se-adequate rats incorporated ⁷⁵Se into glutathione peroxidase within 0.5 hr after ⁷⁵Se injection whereas Se-deficient rats had a lag of 2 to 3 hr before detectable ⁷⁵Se incorporation. After 72 hr, 70 and 50% of the supernatant ⁷⁵Se was incorporated into glutathione peroxidase in Se-adequate and Se-deficient rats, respectively. There were no ⁷⁵Se-labeled fractions in the chromatograms uniquely associated with rats of only one Se status, indicating that Se metabolism was similar in Se-adequate and Se-deficient rats. Cycloheximide injection 30 min prior to ⁷⁵Se injection completely blocked ⁷⁵Se incorporation into liver glutathione peroxidase in both Se-adequate and Se-deficient rats, demonstrating that protein synthesis was required for Se incorporation. These results suggest that large quantities of Se-free, glutathione peroxidase precursor do not accumulate in the liver; these results do not indicate, however, whether Se incorporation occurs during the translational or post-translational phase of protein synthesis.