Abstract:

Objective To probe the influence  of erythropoietin (EPO) on ischemic size and infarction size of  rats with  myocardial ischemia-reperfusion (I/R) injury   and to clarify the mechanism of the protective effect of EOP on myocardial I/R injury.Methods 24 healthy male SD rats were randomly divided into sham-operated group(n=8), I/R group(n=8) and EPO group(n=8).In sham-operated group, the 6-0 thread was passed through the left anterior descending(LAD) coronary artery of rats  without further procedures; in I/R group, the LAD coronary artery were ligated and embedded slack line in the ligature line and reperfusion was performed 45 min later; in EPO group, the rats  had the same surgical procedures as I/R group and were administered by intraperitoneal injection of recombinant human erythropoietin(rhEPO) 5 000 U/kg.The hemodynamic parameters including systolic  pressure(SP), diastolic  pressure(DP),left ventricular systolic pressure(LVSP),left ventricular diastolic pressure(LVDP),left ventricular end-diastolic pressure(LVEDP),maximal rate of increase of ventricular pressure(dp/dtmax ) amd maximal rate of decrease of ventricular pressure  (dp/dtmin)were determined by multiple channel electrophysiolograph after 24 h reperfusion.The apoptotic index of cardiomyocytes was investigated by TdT-mediated dUTP nick end labeling(TUNEL) method.The ischemia and infarction size of hearts were measured by double staining with TTC-Evan’s blue dye.Results After 45 min ischemia and 24 h reperfusion, there were no significant differences in SP,  DP and LVSP between three groups(P>0.05). Compared with sham-operated group, LVDP and LVEDP were significantly increased while dp/dtmax and dp/dtmin were reduced remarkably in I/R group(P<0.05);  compared with I/R group, LVDP and LVEDP were decreased significantly but dp/dtmax and dp/dtmin were increased remarkably in EPO group(P<0.05).The results of the myocardial TUNEL staining revealed that the TUNEL positive cardiomyocytes were increased dramatically after I/R injury;but compared with I/R group, the apoptosis was reduced significantly in EPO group (P<0.05).The results of the myocardium staining showed that the myocardial infarction size was reduced in EPO group compared with I/R group (P<0.05).Conclusion EPO can significantly protect the heart from I/R injury through improving the hemodynamic status and heart function following the reduction of  cardiomyocyte apoptotic and ischemic size as well as infarction size of the left ventricle of the  rats with I/R injury.

Key words: erythropoietin, heart, ischemia-reperfusion injury, hemodynamics, apoptosis, infarction size