Age-associated changes of superoxide dismutase and catalase activities in the rat brain.

Oxygen free radicals have been proposed to be involved in the process of aging. Superoxide dismutase (SOD) and catalase are important for antioxidative defense. In this study, profiles of SOD, catalase, and their mRNA levels were investigated in the frontal, parietal, temporal and occipital lobes, subcortex and cerebellum of male Wistar rats at ages 1-21 months. The total SOD and Mn SOD activities increased with age and exhibited higher levels at 6 and 12 months but decreased thereafter. Activity of catalase showed a similar trend and notably peaked at 12 months. The mRNA levels of Cu/Zn SOD, Mn SOD, and catalase remained constant in all areas tested (frontal, parietal, temporal and occipital lobes, and subcortex) except the cerebellum. Post-transcriptional regulation was involved in modulating the enzymes' activities during aging. Furthermore, the rate of mitochondrial generation of the superoxide anion (O(2)(-).) increased gradually with aging. Taken together, the results suggest that the increase of oxidative potential and the loss of proper antioxidant defense in the rats appear to be highly involved in the aging process of the brain.