Adaptive Response to Swimming Exercise: Antioxidant Systems and Lipid Peroxidation

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Abstract
Enzymatic and nonenzymatic antioxidants play an essential role in protecting tissues from oxidative damage during exercise. The present study investigated the levels of glutathione and antioxidant enzyme systems in the blood of unexercised and exercised (one bout of exhaustive swimming and adapted to swimming endurance training) rats. The hemoglobin concentration, hematocrit, and extent of oxidative injury to red blood cell (RBC) membranes were examined in the above groups of rats. The concentration of reduced glutathione (GSH) in the blood of exercised rats was about 30% higher than in the resting controls (0.40 Å [±] 0.12 GSH/Hb tetramer). Glutathione peroxidase (1.83 Å 0.24 X 102 IU/g Hb), glutathione reductase (1.73 Å 0.44 IU/g Hb), and Superoxide dismutase activities were significantly higher in both groups of exercised rats, whereas catalase activity (8.32 Å 1.04 X 104 IU/g Hb) was similar in the exercised and control animals. The hemoglobin concentration (11.8 g Hb/dL) and hematocrit (39.4%) increased with swimming exercise. Although lipid peroxidation is known to occur following physical exercise, the increased activity of the antioxidant enzymes and cell GSH levels in the present study were able to prevent lipid peroxidation of the RBC membrane. As a result, there was no significant variation in the plasma malondialdehyde levels among the three groups of rats. The redox capacity of the blood may have an important role in the organism in general since the redox status can be transferred across the RBC plasma membrane to other tissues. Exercise training is therefore beneficial to general health and protects cells against deleterious effects of reactive oxygen species produced during physical effort.