EXERCISE TRAINING IMPROVES METABOLIC RESPONSE AFTER ISCHEMIA IN ISOLATED WORKING RAT-HEART

Hearts from treadmill-trained and sedentary rats were perfused in the working heart mode. Mechanical and metabolite status was evaluated bef ore ischemia, after 25 min of global ischemia, and after 30 min of ret rograde reperfusion. After reperfusion, hearts from trained rats were found to have better recovery of contractile function, lower diastolic stiffness, greater efficiency of work, and greater extracellular calc ium responsiveness than hearts from sedentary rats. Training had no si gnificant impact on bioenergetic status before or at the end of ischem ia. However, after reperfusion, both phosphocreatine and ATP were sign ificantly higher in hearts from trained rats than from sedentary contr ol fats. Mitochondrial function in both subsarcolemmal and intermyofib rillar subpopulations was unaffected by ischemia-reperfusion. Ca-45(2) uptake during reperfusion was significantly higher in hearts from se dentary rats than from exercise-trained rats. No differences were foun d in free radical production or tolerance due to training. Therefore, hearts from exercise-trained rats demonstrated an increased metabolic tolerance to ischemic-reperfusion damage, which may contribute to the improved postischemic functional recovery.