Elevated MnSOD is not required for exerciseinduced cardioprotection against myocardial stunning

Physiol 287: H975–H980, 2004. First published March 18, 2004; 10.1152/ajpheart.01208.2003.—Endurance exercise provides cardio-protection against ischemia-reperfusion-induced myocardial stunning and infarction. A recent study demonstrates that an exercise-induced increase in myocardial manganese superoxide dismutase (MnSOD) activity is essential to protect the heart against infarction. It is unknown if an elevation in cardiac MnSOD is also a prerequisite to achieve exercise-induced protection against myocardial stunning. Therefore, this study determined if an exercise-induced increase in myocardial MnSOD activity is a requirement to achieve protection against myocardial stunning. Adult male rats remained sedentary or performed successive bouts of endurance exercise. Hearts were ex-posed to 25 min of global ischemia followed by reperfusion in an isolated working heart preparation. Postischemic recovery of cardiac external work during reperfusion was significantly higher (84 3 vs