Moderate daily exercise is known to be beneficial to health, reducing risks of a number of age-related disorders. Molecular mechanisms that bring about these effects are not clear. In contrast, it has been claimed that some types of prolonged physical exertion are detrimental to health because active oxygen species are generated excessively by enhanced oxygen consumption. Using two age groups of rats, young (4 week) and middle aged (14 months), we investigated the effects of long-term swimming training on the oxidative status of phospholipids, proteins, and DNA. The concentration of thiobarbituric acid reactive substances and 4-hydroxynonenal protein adducts did not differ in the gastrocnemius muscle between exercised and nonexercised animals in the two age groups. The extent of carbonylation in a protein of molecular-weight around 29 KDa and the amount of 8-hydroxydeoxyguanosine in nuclear DNA were smaller (p < .05) in the exercised rats than in the sedentary animals. Activities of DT-diaphorase (CI: 29.3 ± 1.9; C2: 36.1 ± 2.6; El: 27.2 ± 1.3; C2: 33.4 ± 2.9 nmol/mg protein) and proteasome, a major proteolytic enzyme for oxidatively modified proteins were significantly higher in the exercised animals of both age groups (p < .05). The adaptive response against oxidative stress induced by moderate endurance exercise constitutes a beneficial effect of exercise.
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