Abstract: Objective To explore the myocardial protective effects and possible mechanisms of hydrogen sulfide (H2S) on the recovery of ischemic post-conditioning (PC) in the aging rats. Methods Wistar young and aging rats were randomly divided into control group, ischemia/reperfusion (I/R) group, ischemic post-conditioning (PC) group. In addition, aging rats were treated with NaHS (PC+NaHS). The model of myocardial I/R injury and PC in isolated rats hearts was induced with Langendorff system; LDH, CK activities of coronary effluent and SOD activity and MDA content as well as H2S production rate of myocardial tissue homogenate were measured by colorimetric method; Myocardial ultrastructure was detected by transmission electron microscope; The myocardial infarct size was measured by TTC staining; Myocardial cell apoptosis was detected by TUNEL staining; The expression of Bcl-2, caspase-3 and caspase-9 was detected by Western blot. Results Compared with the control group, I/R decreased H2S production rate, SOD activity and CSE expression, increased LDH and CK activity, MDA content, myocardial injury, apoptosis, myocardial infarct size, caspase-3 and caspase-9 and Bcl-2 expression(P<0.01); Compared with the I/R group, PC reduced I/R injury and apoptosis in the young hearts (P<0.01), however, PC lost myocardial protective effect in the aging hearts; Exogenous H2S restored the PC-induced cardioprotection in aging hearts. Conclusion Our results suggest that exogenous H2S restores the myocardial protective effect of PC via anti-oxidation, scavenging free radical and inhibiting apoptosis.

Key words: hydrogen sulfide, ischemia/reperfusion injury, ischemic post-conditoning, apoptosis, aging rats