Superoxide anion generation and the impairment of oxidative phosphorylation yield were studied in rat skeletal muscle mitochondria submitted to
anoxia/reoxygenation in vitro. Production of
superoxide anion was detected after several cycles of
anoxia/reoxygenation. Concomitantly, a decrease of state 3 respiration and phosphorylation yield (
ADP/O) were observed. The latter resulted from a
proton leak. The presence of
palmitic acid during
anoxia/reoxygenation cycles led to a dose-dependent inhibition of
superoxide anion production together with a partial protection of the
ADP/O ratio measured after
anoxia/reoxygenation. The
ADP/O decrease was shown to be due to a permeability transition pore-sustained
proton leak, as it was suppressed by
cyclosporine A. The permeability transition pore activation was induced during
anoxia/reoxygenation by
superoxide anion, as it was cancelled by the spin trap (
POBN), which scavenges
superoxide anion and by
palmitic acid, which induces mitochondrial uncoupling. It can be proposed that the
palmitic acid-induced
proton leak cancels the production of
superoxide anion by mitochondria during
anoxia/reoxygenation and therefore prevents the occurrence of the
superoxide anion-induced permeability transition pore-mediated
proton leak after
anoxia/reoxygenation.