Proton leak and control of oxidative phosphorylation in perfused, resting rat skeletal muscle

The distribution of control over the resting respiration rate (and other variables) was assessed in perfused rat skeletal muscle. The results indicate that the general pattern of control in resting muscle is similar to that seen in isolated rat liver cells (Brown et al. (1990) Biochem. J. 192, 355-362). Control over resting mitochondrial oxygen consumption was distributed between reactions involved in substrate oxidation (flux control coefficient = 0.44 +/- 0.28) and those involved in ATP turnover (0.21 +/- 0.09). The mitochondrial proton leak also had an important share of the control (0.38 +/- 0.21). Since proton leak also has significant control over the resting respiration rate of isolated liver cells and liver and skeletal muscle account for around 60% of the standard metabolic rate of a rat, then these results indicate the potential importance of proton leak as a mechanism of regulating metabolic rate.