Ischemic postconditioning protects aged rat hearts against acute ischemia/reperfusion injury

Objective:The present study was designed to test the hypothesis that IPost protects against I/R injury in aged hearts.Methods:In vivo hearts from adult(3-4 months) Sprague Dawley(SD) rats or aged(16-18 months) SD rats were subjected to 30 minutes ischemia followed by 3 hours of reperfusion.The rats were assigned to one of the following groups based upon the intervention performed(n = 8 per adult group,n = 6 per aged group):(1) I/Radult and I/Raged: received no other intervention either before or after LAD occlu-sion;(2) IPostadult and IPostaged: received ischemic postconditioning induced by four cycles of 10 seconds of ischemia and 10 seconds of reperfusion at the beginning of reperfusion;Shamadult and Shamaged:placement of the silk suture under the LAD and no other intervention.Infarct size,the concentrations of plasma creatine kinase (CK)and lactate dehydrogenase(LDH)were measured.Results:IPost reduced infarct size in both adult SDrats〔(12±1.6)%vs.(30±2.8)%,P0.05〕and aged SD rats hearts〔(14±2.5)%vs.(27±3.5)%,P0.05)〕.There were no significant differences between I/Radult and I/Raged,IPostadult and IPostaged In base-line,the levels of plasma CK in aged groups〔I/Raged:(260±127)U/L vs.IPostaged(254±81)U/L〕werelower than that of adult groups〔I/Radult:(488±160)U/L,I/Radult vs.I/Raged,P0.05〕;〔IPostadult:(476±217)U/L,IPostadult vs.IPostaged,P0.05)〕.But the levels of plasma LDH were no difference between agedand adult groups.Compraed with baseline,the R3h levels of CK[I/Radult:(6 499±2 132)U/L;IPostadult:(3 273±594)U/L;I/Raged:(7 116±2 975)U/L;IPostaged:(4 302±1 408)U/L]and LDH[I/Radult:(1 766±748)U/L;IPostadult:(1 177±430)U/L;I/Raged:(1 829±172)U/L;IPostaged:(1 282±63)U/L]in allgroups were significantly increased(all P0.05).In addition,IPost significantly attenuated the increased lev-els of plasma CK(I/Radult vs.IPostadult,P0.05;I/Raged vs.IPostaged,P0.05)and LDH(I/Radult vs.IPos-tadult,P0.05;I/Raged vs.IPostaged,P0.05)after reperfusion in both adult and aged rats.Conclusion:IPostat onset of reperfusion reduces myocardial infarct size in both adult and aged rat hearts.