Free radicals and cardioplegia. Free radical scavengers improve postischemic function of rat myocardium.

Oxygen-derived free radicals, such as the superoxide (O2-) anion, hydrogen peroxide (H2O2) and the hydroxyl (OH.) radical, may be involved in exacerbating myocardial injury during reoxygenation of ischemic tissue. The naturally occurring antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), prevent the formation of the cytotoxic OH. radical during physiological conditions but may not be able to cope with the free radical generation that follows ischemia and reperfusion. We have used the isolated perfused working rat heart model of cardiopulmonary bypass and ischemic arrest to assess whether exogenous addition of SOD (20 IU/ml) and CAT (100 IU/ml) during ischemia and/or reperfusion can improve postischemic recovery of function following normothermic or hypothermic global ischemic arrest induced by St. Thomas' Hospital cardioplegic solution. Under conditions of normothermia, the addition of SOD alone or CAT alone to both the cardioplegic solution (CS) and the reperfusion solution (RS) had no effect on postischemic recovery (after 20-min working reperfusion) of aortic flow (27.9 +/- 2.7% and 16.1 +/- 6.3%, respectively) when compared with the nontreated control value of 28.1 +/- 3.7%. However, recovery was improved when SOD plus CAT were added to the CS alone (39.3 +/- 8.7%) and was significantly improved when they were added either to both the CS and the RS (48.4 +/- 6.0%; P = less than 0.02) or to the RS alone (51.3 +/- 3.7%; P = less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)