Control of oxidative phosphorylation in rat muscle mitochondria: implications for mitochondrial myopathies.

The control of oxidative phosphorylation has been studied in normal skeletal muscle isolated from the hind legs of rats. The control coefficients of different steps of oxidative phosphorylation on the flux of O2 consumption were determined by the inhibitor method and calculation was done according to the model of Gellerich et al. (FEBS Lett. 274 (1990) 167-170) using a non-linear regression fitting procedure. The respiration was recorded with pyruvate (+malate) and palmitoyl-L-carnitine (+malate) as respiratory substrates, which are the main substrates oxidized in the muscle. It appears that the control is broadly distributed among the different complexes of the respiratory chain, and of the ATP synthesis system. Our results also provide an explanation for the threshold effects often evidenced in the clinical manifestation of mitochondrial diseases.