Generation of hydrogen peroxide by cerebral‐cortex synaptosomes

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Abstract
Guinea‐pig cerebral cortex synaptosomes steadily release H2O2 into the suspending medium, at the rate of 20–30 pmol min−1 mg protein−1. A transient increase of the H2O2 release is induced by the addition of 1 mM Ca2+, which declines within 60–90 s to a rate identical or slightly higher than that before Ca2+. The extra H2O2 following Ca2+ addition varies between 40–100 pmol/mg protein and is insensitive to verapamil. The H2O2 release increases strongly (up to 250 pmol min−1 mg−1) upon depletion of the synaptosomal glutathione by treatment with 1‐chloro‐2,4‐dinitrobenzene, a substrate for glutathione transferase. This treatment however has no effect on the Ca2+‐induced H2O2 transient. In these treated synaptosomes a further increase of the output of H2O2 is rapidly induced upon addition of the Ca2+ ionophore ionomycin. This increase (about 100 pmol min−1 mg−1) lasts several minutes and requires the presence of Ca2+. A similar, though less pronounced increased H2O2 release is obtained (also in the absence of Ca2+) upon depolarization of the synaptosomal plasma membrane with KCI or with veratridine.