Reversible inhibition of electron transfer in the ubiquinol. Cytochrome c reductase segment of the mitochondrial respiratory chain in hibernating ground squirrels.

Electron transfer through the ubiquinol:cytochrome c1-segment of liver mitochondria isolated from hibernating ground squirrels Citellus undulatus is repressed by 70-80% as compared to mitochondria from the active animals. The inhibition site is likely to be localized between ubiquinone and the cytochrome bc1 complex. Partial release of the inhibition can be observed upon swelling of the isolated mitochondria in a hypoosmotic medium, the effect being prevented by phospholipase A2 inhibitors. Possible role of phospholipase A2 in regulation of ubiquinol oxidation by complex bc1 is discussed.