Effects of aging and hyperoxia on oxidative damage to cytochrome c in the housefly, Musca domestica.

Cytochrome c is a component of the mitochondrial electron transport chain, where it transfers electrons from ubiquinol-cytochrome c reductase to cytochrome c oxidase. Autoxidation of some of the components of the electron transport chain is the main source of intracellular O(2)(-*)/H(2)O(2) production in aerobic organisms. Because cytochrome c is located on the outer surface of the inner mitochondrial membrane, it is likely to be constantly exposed to H(2)O(2), secreted by mitochondria into the cytosol. The specific objective of this study was to determine whether cytochrome c in the flight muscle mitochondria of the housefly is oxidatively damaged during aging and/or under severe oxidative stress induced by exposure of flies to 100% oxygen. Results of two independent methods, namely tritiated borohydride labeling for determining carbonylation and mass spectral analysis for the measurement of molecular mass, indicated that neither the carbonyl level nor the molecular mass of cytochrome c was affected by aging or hyperoxia. Thus, either cytochrome c is resistant to oxidative damage in vivo or the oxidized cytochrome c is promptly degraded. These findings also support the concept that protein oxidative damage during aging and under oxidative stress is selective.