Studies on protection by glutathione against lipid peroxidation in rat liver microsomes. Effect of bromosulfophthalein.

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Abstract
The effect of bromosulfophthalein (BSP), an inhibitor of cytosolic glutathione (GSH) S-transferases, on GSH-dependent protection against lipid peroxidation in rat liver microsomes was studied. Microsomal lipid peroxidation induced by ferrous-reduced nicotinamide adenine dinucleotide phosphate (NADPH-Fe2+) or ascorbate was prevented by GSH, and addition of BSP abolished the protective effect of GSH in both peroxidation systems. The effect of BSP seemed to occur at concentrations which inhibited the activity of GSH S-transferase in microsomes.The liberation of free fatty acid hydroperoxides from microsomes during lipid peroxidation ocurred at pH 7.5-8.0. The rate of NADPH oxidation in the system containing peroxidized microsomes, NADPH, GSH, and GSH reductase was significantly higher than that in the system containing normal microsomes, and was inhibited dramatically by BSP and moderately by phospholipase A2 inhibitors. The above findings suggest that microsomal GSH S-transferase may be responsible for GSH-dependent protection against peroxidation, probably via radical scavenging and the cooperative action of microsomal phospholipase A2 and GSH peroxidase activity, which is associated with GSH S-transferase.