INFLUENCE OF EXERCISE AND FIBER-TYPE ON ANTIOXIDANT ENZYME-ACTIVITY IN RAT SKELETAL-MUSCLE

Influence of exercise and fiber type on antioxidant enzyme activity in rat skeletal muscle. Am. J. Physiol. 266 (Regulatory Integrative Comp . Physiol. 35): R375-R380, 1994. - These experiments examined the infl uence of exercise intensity and duration on antioxidant enzyme activit y in locomotor muscles differing in fiber type composition. Nine group s of female Sprague-Dawley rats (age 120 days) exercised 4 days/wk on a motor-driven treadmill for 10 wk. The impact of three levels of exer cise intensity (low, moderate, and high: similar to 55, similar to 65, and similar to 75% of maximal oxygen consumption, respectively) and e xercise duration (30, 60, and 90 min/day) was assessed. Sedentary anim als served as controls. Oxidative capacity in the soleus and white and red gastrocnemius was assessed by measurement of citrate synthase (CS ) activity, and antioxidant capacity was evaluated by assay of total s uperoxide dismutase, catalase, and total glutathione peroxidase (GPX) activities. In all muscles, CS activity increased as a function of exe rcise duration. Furthermore, in the soleus and white gastrocnemius, th e magnitude of the training-induced increase in CS activity was direct ly related to exercise intensity. In contrast, the peak increase in CS activity in the red gastrocnemius was relatively independent of exerc ise intensity. Catalase activity was not increased (P > 0.05) in any m uscle with training. Training-induced changes in superoxide dismutase and GPX activities were muscle specific; specifically, exercise traini ng significantly (P < 0.05) increased superoxide dismutase activity in the soleus as a function of exercise duration up to 60 min/day. Conve rsely, traininginduced significant (P < 0.05) increases in GPX activit y occurred in red gastrocnemius only; the magnitude of the GPX increas e was directly related to exercise duration but relatively independent of intensity. These data demonstrate that exercise training-induced c hanges in muscle antioxidant enzymes are muscle specific.