Endurance training increases the expression of mitochondrial and nuclear encoded cytochrome c oxidase subunits and heat shock proteins in rat skeletal muscle

Cytochrome c oxidase (CCO) is an enzyme complex found on the inner mitochon drial membrane and serves as the final electron acceptor in mitochondrial e lectron transport. Heat shock proteins (HSPs) are involved in the import of nuclear encoded protein subunits into the mitochondria and induce conforma tional changes to form active enzyme complexes. As both the nuclear and mit ochondrial encoded subunits of CCO have been shown to increase in activity and expression in muscle subsequent to artificial loading, and as exercise has been shown to induce HSPs, we sought to determine whether 16-20 weeks o f treadmill exercise would result in enhanced CCO subunit expression, and t o determine if there was a relationship between this expression and HSP con tent in medial gastrocnemius muscle of Fischer 344 rats. Our results indica ted that endurance training resulted in a 53%, 87% and 80% increase (P < 0. 05) in the levels of HSP 60, CCO subunit II and CCO subunit VI. respectivel y. Enzymatic activity of CCO was 84% greater (P < 0.05) after endurance tra ining. Mann Whitney U analyses showed that CCO subunit II and VI increased to the same extent as HSP 60 after endurance training. It appears that 16-2 0 weeks of endurance training leads to uniform increases in CCO subunits an d parts of the transport and assembly mechanisms required for CCO enzyme as sembly. The similarity among the increases in CCO subunits II and VI protei n levels and the increase in CCO enzyme activity suggest that this increase in activity is due to an increase in the amount of CCO enzyme.