Cardioprotective effect of ischemic postconditioning on the model of isolated heart

Irreversible cardiomyocyte damage was induced by 45-min global ischemia followed by 30- min reperfusion in Langendorff-perfused isolated rat heart. Cell damage was assessed by the release of creatine phosphokinase into the perfusate. The hearts were subjected to the following postconditioning protocols: 1) three cycles of 10-sec reperfusion and 10-sec ischemia, total cycle time 20 sec; 2) six cycles of 10-sec reperfusion and 10-sec ischemia, total cycle time 20 sec; 3) three sessions of 20-sec reperfusion and 20-sec ischemia, total cycle time 40 sec; 4) 6 cycles of 20-sec reperfusion and 20-sec ischemia, total cycle time 40 sec; 5) 3 cycles of 30-sec reperfusion and 30-sec ischemia, total cycle time 60 sec. It was found that only postconditioning with a total cycle time of 40 sec or 60 sec prevents myocardial reperfusion injury.