RESUMO
Strenous exercise and high levels of athletic competition may suppress immune function, increasing susceptibility to infections. Infections are often associated with a reduction in athletic performance and can have permanent or lethal consequences. Recent research, however; suggests that regular paraticipation in moderate exercise has an immunoenhancing effect but the mechanism involved remains unknown. This study examined the effect of moderate exercise (70 per cent of maximal oxygen consumption - swimming for 1 hour daily at 32 degrees Celsius with 5 per cent body weight extra load attached to the tail) training on antioxidant enzyme activities and lipid peroxidation in the lymphoid organs (mesenteric lymph nodes, thymus and spleen) and macrophages of rats. This modality of physical effort reduced the content of lipide peroxides in the lymphoid organs. The authors assumed that this effect of exercise training resulted in increased activity of antioxidant enzymes: Glutathione peroxidase in the mesenteric lymph nodes (2.1 fold) and spleen (3-fold), catalase in the spleen (5-fold) and Mn-superoxide dismutase (SOD) in the thymus (28 per cent). The exercise training increased the hydrogen peroxide production and phagocytic capacity in macrophages which was accompanied by a higher Mn-SOD activity. Therefore, a moderate exercise may be the able to improve immune function due to changes in the oxidative metabolism of the lymphoid organs and macrophages.