CARDIOPROTECTIVE EFFECT OF INSULIN-LIKE GROWTH-FACTOR-I IN MYOCARDIAL-ISCHEMIA FOLLOWED BY REPERFUSION

In the present study, the cardioprotective effects of insulin-like gro wth factor I (IGF-I) were examined in a murine model of myocardial isc hemia reperfusion (i.e., 20 min + 24 hr), IGF-I (1-10 mu g per rat) ad ministered 1 hr prior to ischemia significantly attenuated myocardial injury (i.e., creatine kinase loss) compared to vehicle (P < 0.001), I n addition, cardiac myeloperoxidase activity, an index of neutrophil a ccumulation, in the ischemic area was significantly attenuated by IGF- I (P < 0.001), This protective effect of IGP-I was not observed with d es-(1-3)-IGF-I. Immunohistochemical analysis of ischemic-reperfused my ocardial tissue demonstrated markedly increased DNA fragmentation due to programmed cell death (i.e., apoptosis) compared to nonischemic myo cardium. Furthermore, IGF-I significantly attenuated the incidence of myocyte apoptosis after myocardial ischemia and reperfusion, Therefore , IGF-I appears to be an effective agent for preserving ischemic myoca rdium from reperfusion injury and protects via two different mechanism s-inhibition of polymorphonuclear leukocyte-induced cardiac necrosis a nd inhibition of reperfusion-induced apoptosis of cardiac myocytes.