The pH sensitivity of H2O2 metabolism in skeletal muscle mitochondria

• Substrate driven H2O2 consumption shows sensitivity to the pH of the medium.
• Mitochondrial H2O2 efflux rate and %NAD(P)H are also sensitive to the pH of the medium.
• Inconsistencies between H2O2 efflux and %NAD(P)H may be explained by H2O2 consumption.

Mitochondria have the capacity to produce and consume H2O2. We examined H2O2 metabolism in isolated rat skeletal muscle mitochondria and found that the substrate-dependent capacity to consume extramitochondrial H2O2 was markedly higher than the observed rate of H2O2 efflux from mitochondria under the same conditions. The substrate-dependent capacity to consume H2O2 was sensitive to the pH of the medium and we propose that pH related differences in H2O2 consumption pathways may explain inconsistencies we observed between H2O2 efflux rate and the reduction state of the matrix NADH pool.