Objective To investigate the effect of sevoflurane pretreatment on the expression of cystathionine β-synthase(CBS)and heme oxygerase-1(HO-1)during myocardial ischemia-reperfusion(I/R)injury in rats.Methods Thirty adult male SD rats,weighing 180-220 g,were randomly divided into 3 groups(n =10each):sham operation group(group S),I/R group and sevoflurane group(group Sev).Myocardial I/R injury was produced by ligation of the left anterior descending branch of coronary artery for 30 min followed by 2 h reperfusioo.In group Sev,sevoflurane was inhaled before ischemia,the end-tidal concentration was 1.5％-1.7％ and myocardial I/R was produced 60 min later.The rats were sacrificed at 2 h of reperfusion and myocardial tissues were taken for determination of the contents of MDA,GSH,H2S and CO,SOD activity and expression of CBS mRNA and HO-I mRNA.The ultrastructure of myocardium was examined with electron microscope.Results Compared with group S,the contents of MDA,H2S and CO were significantly increased,the expression of CBS mRNA and HO-1 mRNA was up-regulated,and SOD activity and GSH content were significantly decreased in groups I/R and Sev(P ＜ 0.05).Compared with group I/R,the contents of MDA,H2S and CO were significanfly decreased,the expression of CBS mRNA and HO-1 mRNA was down-regulated,SOD activity and GSH content were significantly increased in group Sev.The damage to mitochondrial structure induced by I/R was mitigated by pretreatment with sevoflurane.Conclusion The mechanism by which sevoflurane pretreatment reduces myocardial I/R injury is related to down-regulation of the expression of CBS and HO-1 and decrease in the activities in rats.