Effects of selenium on ribonucleic acid synthesis and degradation in rat liver.

Six groups of weanling rats were fed a low-selenium based diet containing less than 0.01 mg/kg of Se in the diet or the basal diet supplemented with five levels of selenium as selenite (0.1, 0.2, 0.3, 0.4 and 0.5 mg/kg) for at least 16 to 18 weeks. For determination of the effect of selenium on ribonucleic acid (RNA) synthesis in rat liver, rats of each dietary group were injected with a single dose of (5-3H)-uridine, and 3 hours later their livers were removed and subjected to cell fractionation. The radioactivities in the nuclear and cytoplasmic RNA were taken as a measure of the RNA synthesis rate. With selenium supplementation between 0.2 and 0.5 mg/kg diet, the radioactivities, amounts of RNA, as well as RNA/DNA ratios in both nuclear and cytoplasmic fractions of rat liver all increased significantly. In addition, at similar levels of selenium supplementation, statistically significant increments of glutathione peroxidase (GSH-Px) activity and reductions in lipid peroxide in liver were also observed. For assessment of RNA degradation, activities of ribonucleases (RNase) and RNase inhibitor in rats fed the low-selenium diet or a selenium-supplemented diet were determined. The activities of acid RNase and both free and latent alkaline RNase in liver homogenate were not affected by selenium deficiency; however, the level of RNase inhibitor present in the supernatant fraction increased significantly with selenium supplementation at 0.2 mg/kg diet.(ABSTRACT TRUNCATED AT 250 WORDS)