Age-related changes in antioxidant enzymes and prooxidant generation in tissues of the rat with special reference to parameters in two insect species.
The objective of this study was to explore the relationship between partially reduced oxygen species and the aging process. Effect of age on antioxidant defenses and prooxidant generation was evaluated by comparing the activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase, and rates of mitochondrial O-2 and H2O2 generation in the liver, heart, and brain of 3-month and 18-month-old Sprague-Dawley rats. In addition, comparisons of antioxidant defenses and mitochondrial prooxidant generation were made between short-lived insects and the rat tissues. Results indicated that antioxidant enzymes exhibit a mixed pattern of age-related alterations. In each organ of the rat examined, activities of some enzymes were up with age and of others down with age. The overall magnitude of decline in antioxidant defenses observed here and elsewhere in the literature was deemed to be unlikely to be functionally significant. In contrast, the rate of mitochondrial O-2 and H2O2 generation increased in various tissues of the rat. Antioxidant defenses in insects were comparable to tissues in the rat but rates of O-2 and H2O2 generations were notably higher. Results are interpreted to suggest that rates of prooxidant generation may be more crucial than antioxidant levels as possible longevity determinants.