Oxidative stress and aging in the Mongolian gerbil (Meriones unguiculatus)

The objective of this study was to determine if aging in the gerbil, Meriones unguiculatus, is associated with elevation in the level of oxidative stress. Studies were conducted on the brain, heart, kidney, liver and testis of young (3-6 months), adult (15 months), and old (23-25 months) animals. Oxidative damage to proteins, measured as the concentration of protein carbonyls and loss of activity of glucose-6-phosphate dehydrogenase, and to DNA, measured as the concentration of 8-hydroxydeoxyguanosine, increased with age of the animals. There was no appreciable age-related change in the activity of alkaline proteases, which preferentially degrade oxidized protein. Rates of mitochondrial superoxide anion radical and hydrogen peroxide generation also increased with age, most notably in the heart. Antioxidative defenses, measured as activities of superoxide dismutase, catalase and glutathione peroxidase and concentration of glutathione, did not exhibit a uniform pattern of age-related changes. However, when the antioxidative potential of the tissue homogenates was measured as their susceptibility to undergo protein oxidation, in response to experimentally-induced oxidative stress, using X-irradiation, tissues of the old animals were significantly more vulnerable than those of the young animals. Results of this study are interpreted to indicate: (i) that the level of molecular oxidative damage to DNA and proteins increases with age, and (ii) that the increased oxidative damage is due to both an an elevation in the rates of oxidant generation and an increase in the susceptibility of tissues to oxidative damage.