INTRINSIC MYOCARDIAL-FUNCTION AND OXIDATIVE STRESS AFTER EXHAUSTIVE EXERCISE

The purposes of this study were to determine the effect of an exhausti ve running bout on intrinsic myocardial function by using the isolated working rat heart and to determine whether exhaustive exercise result ed in measurable oxidative stress in the myocardium. Untrained familia rized male rats were run at 18 m/min on a 0% grade until exhausted. Ru n time to exhaustion was similar to 75 min. Postexhaustion isolated he art measurements of cardiac output, rate-pressure product at low and h igh workloads, maximum left ventricular pressure, or 50-min performanc e at 85% of peak rate-pressure product were not different from those o f nonexercised perfused control hearts. Exhaustive exercise resulted i n a significant decline (174 vs. 224 nmol/g wet wt; P < 0.05) in nonpr otein nonglutathione sulfhydryls, a thiol fraction indicative of oxida tive stress. However, the magnitude of this measure of oxidative stres s appears insufficient to cause alterations in intrinsic myocardial pe rformance. We conclude that healthy untrained rats subjected to exhaus tive exercise fail to demonstrate accumulation of a functionally signi ficant level of myocardial oxidative stress.