Localization at complex I and mechanism of the higher free radical production of brain nonsynaptic mitochondria in the short-lived rat than in the longevous pigeon

Free radical production and leak of brain nonsynaptic mitochondria were higher with pyruvate/malate than with succinate in rats and pigeons. Rotenone, antimycin A, and myxothiazol maximally stimulated free radical production with pyruvate/malate but not with succinate. Simultaneous treatment with myxothiazol plus antimycin A did not decrease the stimulated rate of free radical production brought about independently by any of these two inhibitors with pyruvate/malate. Thenoyltrifluoroacetone did not increase free radical production with succinate. No free radical production was detected at Complex IV. Free radical production and leak with pyruvate/malate were higher in the rat (maximum longevity 4 years) than in the pigeon (maximum longevity 35 years). These differences between species disappeared in the presence of rotenone. The results localize the main free radical production site of nonsynaptic brain mitochondria at Complex I. They also suggest that the low free radical production of pigeon brain mitochondria is due to a low degree of reduction of Complex I in the steady state in this highly longevous species.