Phospholipid hydroperoxide glutathione peroxidase in various mouse organs during selenium deficiency and repletion

Abstract

An assay for the determination of the newly discovered selenoenzyme, phospholipid hydroperoxide glutathione peroxidase (PH-GPx) in biological material is described. Dietary selenium deficiency and repletion was used as a tool in order to modify this enzyme activity in various mouse organs and to compare it to the activity of the ‘classical’ selenium-dependent glutathione peroxidase (GPx) (EC 1.11.19). A semipurified diet containing less than 12 ppb Se was used for depletion. Controls received this diet supplemented with 500 ppb Se in the form of Na 2SeO 3. The results showed that a rapid loss of GPx activity occurred in liver, kidney and lungs of selenium-deficient mice which reached undetectable levels within 130 days. In the heart, about 24% of control GPx activity was still present. In contrast, PH-GPx activity was more slowly depleted by Se deficiency and resulted in residual activities ranging from 30 to 70% in the different organs ever after 250 days of depletion. In repletion experiments with a single application of 10 or 500 μg/kg Se, only the high dose restored either enzyme activity. The data demonstrate that the need for selenium of the two glutathione peroxidases is different. A markedly distinct organ distribution of both enzymes suggests that the heart may be the organ most sensitive to oxidative stress.