Species, Tissue and Subcellular Distribution of Non Se-Dependent Glutathione Peroxidase Activity

Abstract

Glutathione peroxidase has been recognized as a Se containing enzyme and its activity can be reduced in many organs and tissues of animals by feeding a Se deficient diet. Measurement of glutathione peroxidase activity has accordingly, been used to assess nutritional selenium status. Separation of rat liver glutathione peroxidase activity into a selenium-dependent component and a non selenium-dependent one has been recently described. To gain insight into the possible physiological role of the non Se-dependent glutathione peroxidase and its possible interference in the assessment of nutritional Se status, its presence in a number of tissues of the rat, in the livers of several different species, and in the subcellular fractions of rat liver has been studied. The two glutathione peroxidase activities were measured in 105,000 × g supernatants after separation by Sephadex G-150 chromatography. In the six tissues of the rat found to contain the non selenium-dependent activity, the percentage of the total glutathione peroxidase accounted for by it ranged from 23% in fat to 91% in testis. Livers from all of the seven species examined contained non Se-dependent glutathione peroxidase activity. The percentage of the total liver glutathione peroxidase activity accounted for by this activity ranged from 35% in the rat to 100% in the guinea pig. Non Se-dependent glutathione peroxidase activity was confined to the soluble fraction of rat liver. These findings show that variable amounts of non selenium-dependent glutathione peroxidase are present in a number of tissues. Thus, assessment of nutritional selenium status by measurement of glutathione peroxidase activity in these tissues using organic hydroperoxides as substrates will be erroneous.