The aim of the study was to evaluate the interplay between mitochondrial respiration and H2O2 release during the transition from basal non-phosphorylating to maximal phosphorylating states. We conducted a large scale comparative study of mitochondrial oxygen consumption, H2O2 release and electron leak (% H2O2/O) in skeletal muscle mitochondria isolated from mammal species ranging from 7 g to 500 kg. Mitochondrial fluxes were measured at different steady state rates in presence of pyruvate, malate, and succinate as respiratory substrates. Every species exhibited a burst of H2O2 release from skeletal muscle mitochondria at a low rate of oxidative phosphorylation, essentially once the activity of mitochondrial oxidative phosphorylation reached 26% of the maximal respiration. This threshold for ROS generation thus appears as a general characteristic of skeletal muscle mitochondria in mammals. These findings may have implications in situations promoting succinate accumulation within mitochondria, such as ischemia or hypoxia.
Keywords: Allometry; Bioenergetics; Oxidative phosphorylation; Radical oxygen species; Skeletal muscle.
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