Oxygen Radicals Released During Ischemic Preconditioning Contribute to Cardioprotection in the Rabbit Myocardium

Previous studies have proposed that oxygen radicals may play a role in the triggering of ischemic preconditioning. However, studies evaluating the effects of radical scavengers have yielded conflicting results, possibly because of differences in the number of preconditioning episodes used. The present study tested whether N-2-mercaptopropionylglycine (MPG) could block protection of both single and multiple episodes of preconditioning inin situandin vitrorabbit hearts. All hearts were subjected to 30 min of regional ischemia followed by reperfusion for 2 (in vitro) or 3 (in situ) h. Infarct size was measured by tetrazolium. Infarction in controlin situhearts was 37.5±3.5% of the risk zone. A single cycle of preconditioning (PC1), with 5 min ischemia/10 min reperfusion, reduced infarct size to 12.3±2.0% (P