Voluntary wheel running prevents the acidosis‐induced decrease in skeletal muscle mitochondrial reactive oxygen species emission

What is it about?

Strenuous exercise promotes muscle adaptation and generally acidifies skeletal muscles (lowers muscle pH). Muscle acidification has been shown to affect the function of muscle mitochondria, which have a crucial role in energy supply (phosphorylation) through the electron transport system (ETS), and in adaptive signalling pathways. However, changes in mitochondrial function with lower pH have only been shown in untrained muscle, and therefore the effects of acidification is unknown for trained skeletal muscle. Here we used voluntary wheel running to exercise rats, and then investigated mitochondrial function across a range of pH in exercised and non-exercised rats. Exercised rats had greater activity of metabolic enzymes associated with energy release, and greater mitochondrial oxygen consumption. In both groups, lowering pH decreased mitochondrial free radical production in non-phosphorylation states. However, when electron flow through the ETS was maximised, acidification lowered free radical production in non-exercised rats, but had no effect in exercised rats. We then tested the effects of acidification on ETS components, and found that one enzyme, complex III of the ETS, is less sensitive to changes in pH in exercised rats in comparison to non-exercised rats. Our results suggests there may be a mechanism by which pH directly affects ETS and specifically Complex III function, and training may alter this response.

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