Exercise and endogenous antioxidant enzyme activity in perfused and ischemic cardiac tissue

Abstract

Endogenous antioxidant enzymes such as catalase (CAT), glutathione peroxidase (GPx), and the superoxide dismutase isoforms (SOD) prevent ischemia reperfusion (IR)‐generated oxidative stress during IR. The contribution of these antioxidant enzymes to redox balance in perfused and ischemic tissues from exercised hearts is unknown. This investigation, used 4 month old male SD rats, to examine CAT, GPx, and SOD in perfused and ischemic regions of exercised and sedentary hearts. Treadmill exercise (3×60m/day) was used to precondition against IR injury. Animals were exposed to either a short duration (20mI/30mR) or long duration (50mI/120R) IR challenge. Evans blue infusions denoted perfused and ischemic tissue. ECG analysis and TTC staining indicated significant IR injury in sedentary hearts. Exercise partially prevented IR‐generated ECG arrhythmias and necrosis. MnSOD activity was elevated by exercise in both perfused and ischemic tissue exposed to short duration IR, but only in perfused tissue exposed to long duration IR. Cardiac protein carbonyl content was elevated in ischemic tissue from sedentary but not exercised hearts. These data demonstrate that MnSOD remains elevated in both ischemic and perfused cardiac tissue during short duration IR, but is depleted by longer duration IR. (JQ ‐ HL087256)