Age-related changes in activities of mitochondrial electron transport complexes in various tissues of the mouse

The purpose of the present study was to examine the role of mitochondria in the aging process by determining whether the activities of various electro n transport chain oxidoreductases are deleteriously affected during aging a nd whether the hypothesized age-related alterations in different tissues fo llow a common pattern. Activities of respiratory complexes I, II, III, and IV were measured in mitochondria isolated from brain, heart, skeletal muscl e, Liver, and kidney of young (3.5 months), adult (12-14 months), and old ( 28-30 months) C57BL/6 mice. Activities of some individual complexes were de creased in old animals, but no common pattern can be discerned among variou s tissues. In general, activities of the complexes were more adversely affe cted in tissues such as brain, heart, and skeletal muscle, whose parenchyma is composed of postmitotic cells, than those in the liver and kidney, whic h are composed of slowly dividing cells. The main feature of age-related po tentially dysfunctional alterations in tissues was the development of a shi ft in activity ratios among different complexes, such that it would tend to hinder the ability of mitochondria to effectively transfer electrons down the respiratory chain and thus adversely affect oxidative phosphorylation a nd/or autooxidizability of the respiratory components. (C) 2000 Academic Pr ess.