Possible involvement of erythropoietin in remote renal preconditioning-induced cardioprotection in rats

Remote preconditioning is a unique phenomenon in which brief episodes of ischemia and reperfusion to remote organs protect the target organ against sustained ischemia/reperfusion (I/R)induced injury. Protective effects of remote renal preconditioning are well established in the heart, but their mechanisms still remain to be elucidated. Hence, the present study was designed to investigate the possible involvement of erythropoietin in remote renal preconditioning (RRPC)-induced cardioprotection in rats. RRPC was performed by 4 episodes of 5 min renal artery occlusion followed by 5 min reperfusion. Gentamicin (100 mg/kg intraperitoneal) was administered for 6 days for induction of renal failure. Isolated rat hearts were perfused on Langendorff apparatus and were subjected to global ischemia for 30 min ischemia followed by 120 min reperfusion. The levels of lactate dehydrogenase (LDH) and creatine kinase (CK) were measured in coronary effluent to assess the degree of myocardial injury. Extent of myocardial infarct size and coronary flow rate was also measured. RRPC prevented I/R-induced myocardial injury and produced cardioprotective effects. However, cardioprotective effects of RRPC were not observed in renal failure rats, indicating the protective role of humoral factor was released from functional kidneys. In renal failure rats, exogenous administration of rhEPO (5000 IU/kg intraperitoneal) with RRPC restored the cardioprotective effects of later. These results implicate that RRPC-induced cardioprotective effects may be mediated through release of erythropoietin from kidney.