Effects of age and glutathione levels on oxidative stress in rats after chronic exposure to stretch-shortening contractions

We investigated effects of age and glutathione synthesis inhibition on the oxidative stress status of tibialis anterior muscles from young and old Fisher 344 × Brown Norway male rats after chronic administration of stretch-shortening contractions. Oral supplementation of l-buthionine-(S,R)-sulfoximine (BSO) inhibited glutathione synthesis. Dorsiflexor muscles in the hindlimb were exposed to 80 maximal stretch-shortening contractions (SSCs) three times per week for 4.5 weeks. We measured malondialdehyde, hydrogen peroxide (H2O2), and free isoprostanes to determine oxidative stress. Glutathione peroxidase activity was measured as an indicator of H2O2 scavenging. Glutathione measurements confirmed the effectiveness of BSO treatment. In young rats, the SSC exposure protocol prevented oxidative stress and enhanced H2O2 scavenging. In old rats, malondialdehyde was increased in the exposed muscle and a BSO-induced increase in H2O2 was not alleviated with SSC exposure as seen in young rats. In addition, glutathione peroxidase activity and total glutathione were increased in old rats relative to their young counterparts. All comparisons were significant at the 0.05 level. Overall, BSO administration was effective in decreasing total glutathione levels and increasing H2O2 levels in old and young rats exposed to SSCs. In addition, effects of chronic exposure to high-force resistive loading SSCs in active muscle from old animals are: (1) antioxidant capacity is enhanced similar to what is seen with endurance training and (2) oxidative stress is increased, probably as a consequence of the enhanced vulnerability due to aging.