AGE-RELATED-CHANGES OF THE MITOCHONDRIAL ENERGY-METABOLISM IN RAT-LIVER AND HEART

The influence of aging on mitochondrial energy metabolism of rat liver and rat heart has been studied by analysis of (i) respiratory rate of succinate-supplemented mitochondria in state III (coupled state in the presence of ADP + Pi); (ii) the rate of synthesis of ATP in succinate-supplemented mitochondria; (iii) the ATP hydrolase activity of sonicated submitochondrial particles. The results indicate a decrease of the F0F1-ATP synthase activity in mitochondria isolated from both organs of aged (24-month-old) as compared to young (3-month-old) rats which was accompanied by a decrease of immunodetected amount of the beta-F-1 (subunit of the catalytic F-1 sector of F0F1-ATP synthase). These effects were more evident in heart than in liver mitochondria. Analysis of the mitochondrial content of glutathione (GSH), an essential intracellular antioxidant agent, shows a decrease in mitochondria of both tissues of aged animals. Exposure of submitochondrial particles to free radicals, produced either by Co-60 or by respirtory chain (in presence of the inhibitor antimycin A) mimicked the alterations of F0F1 ATP synthase observed in submitochondrial particles of aged rats. The possible relationship between aging process, free radical production and alteration of mitochondrial oxidative phosphorylation is discussed.