Protective Effects And Mechanisms Of Erythropoietin On Myocardial Ischemia/reperfusion Injury In Rabbits

【Objective】To establish myocardial ischemia/reperfusion(I/R) injury models of New Zealand rabbits,and to investigate the influence of Erythropoietin on cardiac myocyte apoptosis and the expressing level of Caspase-3 protease which is critical in apoptosis in ischemia/reperfusion injury rabbits in order to explore the protective effects of Erythropoietin on myocardial ischemia/reperfusion injury rabbit and its mechanisms of action.So to further provide theoretical basis for the clinical reasonable application of Erythropoietin.Sixteen New Zealand rabbits,male,weighing 2.0±0.2kg,were randomly divided into two groups:①ischemia/reperfusion injury group(I/R group,control group)②Erythropoietin group(EPO group,drug group).Rabbits were subjected to a 60 minutes of left anterior descending coronary artery(LAD) occlusion followed by reperfusion for 180 minutes to establish rabbit myocardial ischemia/reperfusion injury models.When the left anterior descending coronary arteries were ligated,recombinant human Erythropoietin(recombinant human EPO,rhEPO) were injected at a dose of 1000 U/kg in rabbits of EPO group through the ear vein,the rabbits of control group were injected saline equivalently.1,2 ml internal jugular vein blood were collected at the following points:5 minutes before occlusion,60minutes after occlusion,60 minutes and 180 minutes after reperfusion.Serum abstracted from the blood for testing the concentration of CK-MB by Automatic Biochemical Analyzer.2,At 180 minutes after reperfusion, the corresponding ischemic myocardium was brought to made paraffin sections.3,The apoptotic index of myocardial cell and the level of Caspase-3 in ischemic region were tested by immunohistochemical methods.4,The specimens of light microscope and electron microscopy were made to observe the general myocardial tissue morphosis and ultramicro organizational structure.【Results】The Serum CK-MB concentration increased gradually with protraction of the ischemia and reperfusion time(P＜0.01).Before ischemia the serum CK-MB concentration were no significant difference between EPO group and the I/R group(P＞0.05).The increased level of CK-MB concentration in EPO group were markedly lower than those in the I/R group at 60 minutes after ischemia,60 minutes after reperfusion and 180 minutes after reperfusion.The difference was statistically significant (P＜0.01,P＜0.01,P＜0.01).Compared to the I/R group,both the ischemic myocardial apoptotic index and the expressing level of Caspase-3 in EPO group decreased significantly(P＜0.01,P＜0.01).The impaired changes of the general morphosis and the ultrastructure at myocardial ischemia/reperfusion injury areas in the I/R group were severer than that in the EPO group.【Conclusions】1,EPO has visible protective effects on the myocardial ischemia/reperfusion injury rabbits.The mechanism of cardioprotection may be associated with stabilizing the myocardium cell membrane structure to decrease the release of myocardial enzyme and inhibit cardiac myocyte apoptosis.2,Myocardial ischemia/reperfusion injury induce cardiac myocyte apoptosis.EPO can inhibit cardiac myocyte apoptosis accompanied by reducing the expression of Caspase-3 which is critical in apoptosis.That suggests EPO can inhibit the cardiac myocyte apoptosis induced by ischemia/reperfusion injury through downregulation of the Caspase-3 protein expression.