Effect of exercise training on the ability of the rat heart to tolerate hydrogen peroxide.

OBJECTIVE The purpose of this study was to determine whether exercise training could precondition the myocardium against hydrogen peroxide (H(2)O(2))-induced damage. METHODS Male Fischer 344 rats ran on a treadmill for 9 weeks (60 min/day, 22 m/min, 6 degrees grade, 5 days/week). Isolated perfused working hearts from exercise trained (ET, n=8) and sedentary (SED, n=10) animals were perfused with 150 microM H(2)O(2). RESULTS Pre-H(2)O(2) baseline values for cardiac external work (COxSP), coronary flow (CF), and lactate dehydrogenase (LDH) release were similar between groups. At 5 min of H(2)O(2), COxSP was unchanged from baseline but CF was increased 30% in SED and 46% in ET (P<0.05 vs. SED). COxSP began to decline similarly thereafter in both groups, dropping to 20% of baseline at 20 min. CF in ET remained higher than SED throughout (P<0.05). LDH leakage remained near baseline during the first 15 min of H(2)O(2) exposure, but was elevated (P<0.05) 72% in SED and 40% in ET after 20 min, and was 2.2-fold greater in SED than ET (P<0.05) after 25 min. Heat shock protein 70 was 2.1-fold greater in ET than SED (P<0.05), but ET did not change catalase and glutathione peroxidase. CONCLUSIONS The results of this study indicate that chronic moderate exercise will enhance coronary flow and attenuate the development of myocardial injury when exposed to H(2)O(2), but will not affect H(2)O(2)-induced decrease in pump function.