Age and gender differences in antioxidant enzyme activity: potential relationship to liver carcinogenesis in male mice.

The present study was undertaken to determine whether age- and gender-related changes in lipid peroxidation (LPO) were attributable to differences in hepatic antioxidant defense mechanisms of aging 1-, 4-, 10-or 18-month-old male and female CBA mice. Specifically, total superoxide dismutase (tSOD), glutathione peroxidase (Gpx) and catalase (CAT) activities were examined. As an indicator of liver oxidative damage, we determined LPO, expressed in terms of thiobarbituric acid reactive substances (TBARS). LPO increased in both sexes with age. tSOD seems to be a relatively inert antioxidative enzyme in both sexes of mice. The main changes in antioxidant capacity of mice liver during aging were associated with sex-related CAT and Gpx increments observed in males but not in females. Surprisingly, more than 60% of 18-month-old males (but none of females) which started to appear at 10-months developed hepatic tumors. The results show that (1) the increased liver antioxidant capacity of CAT and Gpx in male mice might be a sign of oxidative stress; (2) the increase in CAT and Gpx activities in male mice is strongly correlated with incidence of hepatic tumors; (3) the significantly increased SOD activity in tumor-bearing mice might have induced damage with accumulated hydrogen peroxide H2O2.