Effect of exercise training on antioxidant and metabolic functions in senescent rat skeletal muscle.

Aging is known to be associated with alterations of both oxidative capacity and antioxidant status in skeletal muscle. In the present investigation we compared the activity of enzymes involved in both metabolic functions and antioxidant defense capacity in young adult (5 months old) and senescent (27.5 months old) Fischer 344 rats. In addition, we studied the effects of chronic exercise training on these enzymes in the senescent skeletal muscle. Old sedentary rats had significantly lower glutathione peroxidase (GPX) activity (-22%, p less than 0.05) in the deep portion of vastus lateralis muscle (DVL) than young sedentary rats, but after a progressive 10-week treadmill training program GPX activity in DVL was significantly increased in old rats to a level higher than that seen in young sedentary rats. Superoxide dismutase and catalase activities in the DVL were not altered significantly with aging or by training. Glutathione S-transferase activity in the same muscle was elevated (p less than 0.05) with aging but unaffected by training. Citrate synthase and malate dehydrogenase activities in the DVL muscle were significantly decreased in senescence, whereas training increased these two enzyme activities by 71 and 48%, respectively (both p less than 0.05). Lactate dehydrogenase activity in the same muscle decreased with age but increased 23% (p less than 0.05) in old rats. These data indicate that while aging may significantly affect antioxidant and metabolic capacities in skeletal muscle, regular exercise can preserve functions of these enzyme systems at old age.