Studies on the regulation of glutathione peroxidase activity

Abstract Glutathione peroxidase(GSH-Px) is known to be a seleno-enzyme whose activity is proportional to the amount of dietary selenium (Se). In this study, a possible mechanism of Se-induced increase of GSH-Px activity was investigated in various tissues of Se deficient rats. Further, the relationship between GSH-Px and glutathione S-transferase(GSH-ST) having GSH-Px like activity was also examined. Se deficiency produced marked decrease of both Se content and GSH-Px activity in various tissues. Under these conditions, marked increase of GSH-ST activity in the liver, kidney and duodenal mucosa was found. The injection of selenite (1.0 μmol/kg, s.c.) equivalent to the amount of daily Se intake produced time-dependent increase of GSH-Px activity in every tissue except brain and heart, suggesting stimulated biosynthesis of GSH-Px; but the increased activity of GSH-ST in Se deficient rats was restored within 48 hr after selenite injection. Further, Se-induced increase of GSH-Px activity in the liver was markedly suppressed by phorone(250 mg/kg, i.p.), a GSH depleting agent. A similar effect was also observed in livers of rats treated with diethylmaleate(500 mg/ kg, i.p.), but there was no suppression in other tissues. Present findings suggest that GSH plays a role in the biosynthesis of GSH-Px in the liver and that GSH-ST functions as a substitute for GSH-Px in Se deficient rats.