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 cytoc hrome c oxidase. Autoxidation of some of the components of the electron tra nsport chain is the main source of intracellular O-2(-.)/H2O2 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 H2O2, secreted by mitochondria into the cytosol. The specific objective of this study was to determine whether cytochrome c in the flight muscle mito chondria of the housefly is oxidatively damaged during aging and/or under s evere oxidative stress induced by exposure of flies to 100% oxygen. Results of two independent methods, namely tritiated borohydride labeling for dete rmining carbonylation and mass spectral analysis for the measurement of mol ecular mass, indicated that neither the carbonyl level nor the molecular ma ss of cytochrome c was affected by aging or hyperoxia. Thus, either cytochr ome 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. (C) 2000 Elsevier Science Inc.