Bromosulfophthalein abolishes glutathione-dependent protection against lipid peroxidation in rat liver mitochondria.

The effect of bromosulfophthalein (BSP) on GSH-dependent protection against lipid peroxidation in rat liver mitochondria was examined. Mitochondrial lipid peroxidation induced by ascorbate-Fe2+ was prevented by GSH, and addition of BSP abolished the protective effect of GSH. The effect of BSP was apparently not due to causing disappearance of GSH from the reaction mixture by interacting directly with GSH. BSP strongly inhibited the mitochondrial GSH S-transferase activity rather than the GSH peroxidase activity. Ascorbate-Fe2+-induced lipid peroxidation in mitochondria without addition of GSH was also stimulated to some extent by BSP, and the stimulation seems likely to be due to abolition of the inhibitory effect of endogenous GSH. GSH could not be replaced as an inhibitor of lipid peroxidation by cysteine, beta-mercaptoethanol, or dithiothreitol. The inhibitory effect of GSH on lipid peroxidation was not observed in vitamin E-deficient mitochondria. No inhibitory effect of exogenous vitamin E was demonstrated either in vitamin E-deficient mitochondria or in vitamin E-sufficient mitochondria in the presence of BSP, whether GSH was added or not. These results indicate that a mitochondrial GSH-dependent factor which inhibits lipid peroxidation requires vitamin E to exert its function. It is suggested that mitochondrial GSH S-transferase(s) may be responsible for GSH-dependent inhibition of lipid peroxidation in mitochondria, probably by scavenging lipid radicals.