SHORT-TERM TRAINING IMPROVES SKELETAL MUSCLE BUT NOT MYOCARDIAL PROTECTION AGAINST OXIDATIVE INJURY IN VITRO

Abstract

391 Chronic endurance exercise can improve the endogenous antioxidant defense and reduce tissue lipid peroxidation within the myocardium and skeletal muscle. It is unknown whether short-term training can confer these same benefits. We tested the hypothesis that 5 consecutive days of endurance exercise would elevate both enzymatic [glutathione peroxidase (GPX)] and non-enzymatic [glutathione (GSH)] antioxidant defenses within skeletal muscle and the myocardium. Further, we postulated that this increase in antioxidant defense would protect these tissues from lipid peroxidation following exposure to H2O2 and OH radicals in vitro. Male Sprague-Dawley rats were treadmill trained [N=8 (T)] for 5 consecutive days (25/min, 0% grade for 60 min). Sedentary rats served as controls [N=8 (C)]. Training did not alter (p>0.05) GPX activity in the heart but GPX activity was increased (p<0.05) in the GAST of the T vs C (1.29 vs 1.91 umol/g/min). Further, GSH concentration increased (p<0.05) in the GAST of T animals compared to C. In contrast, training did not alter (p>0.05) the GSH content of the heart. Basal lipid peroxidation, evidenced by thiobarbituric reactive acid substances (TBARS), was greater (p<0.05) in the GAST and hearts of the C compared to T (31.1 vs 21.6 and 58.0 vs 44.7 nmol/g wet wt, respectively). Following exposure to H2O2 and OH radicals in vitro, TBARS content was higher in the GAST of the C compared to T (p<0.05, 31.9 vs 23.4, 35.6 vs 20.4 nmol/g wet wt, respectively). There were no differences between T and C in heart TBARS following the oxidative challenges in vitro. These data suggest that short-term exercise training can improve the enzymatic and non-enzymatic antioxidant defenses within skeletal muscle. In contrast, we conclude that the myocardium requires a greater exercise training duration to increase its antioxidant defenses to protect against H2O2 or OH-mediated oxidative injury. Sponsored by the American College of Sports Medicine Research Foundation (HKV)