GLUTATHIONE STATUS AND REACTIVE OXYGEN GENERATION IN TISSUES OF YOUNGAND OLD EXERCISED RATS

The effects of exercise on the generation of active oxygen species and radical-scavenging capacity were studied in physically active and sed entary young and old rats. Exercise increased the hydroxyl radical con tent in all tissues of physically active young rats, except in the pla sma. In old rats, the basal level of the radical increased significant ly in plasma, heart, and skeletal muscles, but decreased in liver; and physical activity decreased it to that of young rats in most cases. W ith exercise, the content of reduced glutathione increased in plasma, heart, and skeletal muscles of young rats, whereas that of oxidized gl utathione markedly decreased in liver and increased in brain and white gastrocnemius muscle. The total glutathione levels in these tissues c hanged in a similar way, indicating that glutathione was released from the pool in the liver. In rats allowed to run voluntarily for 5 weeks , the effects were more pronounced than in the sedentary rats, The rat io of reduced to total glutathione, which indicates the capacity to re duce glutathione, increased in plasma, heart, and soleus muscle of sed entary young rats after exercise, and increased further in those under going physical activity. In old rats, the reduced glutathione level in creased in plasma, heart, liver, and brain, even though the total decr eased. These results suggest that physical activity enhances the endog enous ability to defend against oxidative stress. In old rats, even th ough glutathione synthesis is decreased, the regenerating capacity see ms to be increased in order to compensate for the increased oxidative stress.