Pathways of hydrogen peroxide generation in guinea pig cerebral cortex mitochondria

The production of H2O2 by brain mitochondria was monitored employing a new technique based on the horseradish peroxidase dependent oxidation of acetylated ferrocytochrome c. It was shown that brain mitochondria release H2O2 by an intermediate autooxidation at the QH2-cytochrome c oxidoreductase level (induced by antimycin A and inhibited by myxothiazol). With both succinate and pyruvate plus malate this H2O2 release is inhibited at high substrate concentrations. With pyruvate plus malate a second source of H2O2 could be detected, apparently from autoxidation at the NADH dehydrogenase level. With alpha-glycerophosphate some H2O2 derives from autooxidation at the alpha-glycerophosphate dehydrogenase. The NADH dehydrogenase dependent, but not the QH2-cytochrome c oxidoreductase dependent H2O2 was significantly stimulated upon depletion of the mitochondrial glutathione.