Oxygen toxicity in cultured aortic endothelium: selenium-induced partial protective effect

The time course of biochemical changes related to cell loss and damage during exposure to 95% O2 [DNA and protein content of dishes, lactate dehydrogenase (LDH) release] was studied in postconfluent endothelial cells isolated from pig aorta, cultured in standard medium and in medium supplemented with 2 X 10(-7) M selenomethionine (Se-Met). A fourfold increase in glutathione peroxidase (G-Px) was the only major enzymatic Se-related effect under both normoxic and hyperoxic conditions, the other antioxidant enzymes being little or not at all affected by this treatment. The addition of Se-Met had a clearcut protective action against the cytotoxic effect of O2 as shown by measurements of DNA and protein content of Petri dishes and of LDH release. On the other hand, the most sensitive O2-related effect, namely the decrease in [3H]thymidine incorporation into DNA, was not affected by Se-Met addition. These experiments suggest that some of the O2-related toxic effects (but not the inhibition of DNA synthesis) could be mediated by lipid peroxides, since they were, at least partly, prevented by a Se-Met-induced increase in G-Px activity.