Abstract: Objective:To observe the portective effect of levosimendan(Levo) in cardioplegic soIution on isoIated rat heart. Methods:Thirty-two male Wistar rats were randomly divided into four groups(n=8 in each group): no Levo(L0), 0.03μmol/L Levo(L0.03), 03μmol/L Levo(L0.3), 03μmol/L Levo and 10μmol/L glibenclamide(LG) in St.ThomasⅡ(STH-2)cardioplegia solution.The hearts was connected to Langendorff perfusion apparatus immediately.After perfused with K-H solution for 30 minutes,perfuseed by different cardioplegic solution at 25℃ for 2 hours,and then were reperfused with K-H solution for 30 minutes. Observed the changes of hemodynamics,myocardial enzyme leakage in the coronary effluent.Results: There were no significant diferences in hemodynsmics, creatine kinase（CK）and lactate dehydrogenase（LDH）before hearts stopped beating in all groups(P>0.05).After reperfusion ,the recovery of myocardial hemodynamic parameters in group L0.3 better than other groups(P<0.01 or P<0.05).LDH and CK significant dcreease in group L0.03 compared with other groups (P<0.05)..Conclusion: Levo added into STH-2 cardioplegic soIution has protective effects on myocardial isehemia-reperfusion injury，the mechanism of the protection may be related to the opening of the adenosine triphosphate-regulated potassium channel (KATP).

Key words: levosimendan, cardioplegic soIution, rats, cardioprotective effect, ischemic-reperfusion injury, KATP channel