[Effect of thiamylal on superoxide generation in the cells and on lipid peroxidation of biological membranes].

The effect of thiamylal on the cellular superoxide generation and on membrane lipid peroxidation was examined. Active oxygens may play an important role in lung oxygen toxicity, since they attack the biological membranes and cause their lipid peroxidation. These active oxygens are generated in intra- and extra-cellular spaces in vivo. Under a certain condition, main part of intracellular superoxide generation is dependent on mitochondrial electron transport system. In this study, this superoxide generation was inhibited by the treatment with a low concentration of thiamylal concomitant with the uncoupling of mitochondrial oxidative phosphorylation. On the other hand, most part of extracellular superoxide is generated by the stimulation of phagocytotic cells such as neutrophils. This superoxide generation was also inhibited by the modification of cell membrane with thiamylal. Furthermore, the lipid peroxidation of mitochondria induced by Fe2+ was inhibited by the drug. Similar inhibitory action of the drug was observed on the superoxide dependent lipid peroxidation of Vitamin E deficient rat erythrocyte ghost or of phosphatidylinositol containing liposomal membranes. From these results, it was concluded that the thiamylal might act as a protective agent against the lung oxygen toxicity.