The measurement of radioactivity in liquid samples with a modified marinelli beaker

Abstract

Selenium (Se)-glutathione peroxidase activities were measured using H2O2 as a substrate in retina, retinal pigment epithelium (RPE), lens, brain, liver and testes from rats either deficient or supplemented with vitamin E and selenium for 20–30 weeks. In the supplemented rats, the RPE was found to be particularly rich in Se-glutathione peroxidase activity, being second only to liver in specific enzyme activity. Non-Se-glutathione peroxidase activities were also estimated in the same tissues utilizing an organic hydroperoxide substrate. Except for the retina and testes, only the Se-glutathione peroxidase activity could be detected to any significant extent in tissues from rats fed the supplemented diet. In rats fed the deficient diet there is a large decrease in the Se-enzyme activity for all tissues examined except brain. Except for brain and perhaps testes, tissues from deficient rats also show an increase in the fraction of non-Se-enzyme activity contributed to total glutathione peroxidase activity. For RPE and testes, the ratio of non-Se-enzyme activity to Se-enzyme activity is estimated to be about one-tenth the ratio found in other tissues examined in the deficient rats.In a previous publication (Katz, Stone and Dratz, 1978) we have shown that RPE and testes from vitamin E and Se deficient rats are particularly sensitive to the accumulation of a yellow autofluorescent pigment which is thought to be indicative of lipid peroxidation. Other retinal tissues, as well as brain and liver, accumulate much less of this pigment. The relatively low ratio of non-Se-enzyme to Se-enzyme activity observed in the RPE and testes of deficient rats may be related to the apparent susceptibility of these tissues to lipid peroxidation.