Objective To evaluate the effect of dexmedetomidine on myocardial injury induced by renal ischemia-reperfusion (I/R) injury in rats.Methods Twenty-four male Wistar rats,weighing 280-300 g,were randomly divided into 3 groups (n =8 each):sham operation group (group S),group I/R and dexmedetomidine group (group Dex).Renal ischemia was induced by occlusion of bilateral renal arteries for 45 min followed by reperfusion in I/R and Dex groups.At 20 min before ischemia,dexmedetomidine 50 μg/kg was injected intraperitoneally in group Dex,and the rest procedures were similar to those previously described in group I/R.The rats were sacrificed at 24 h of reperfusion and myocardial specimens were obtained for determination of malondialdehyde (MDA) content and superoxide dismutase (SOD) activity.The apoptosis in cardiomyocytes was examined by flow cytometry.Apoptosis index was calculated.The expression of Bcl-2 and Bax was detected by immunohistochemistry,and Bcl-2/Bax ratio was calculated.Results Compared with group S,apoptosis index and MDA content were significantly increased in I/R and Dex groups,Bcl-2/Bax ratio was decreased in group I/R,and Bcl-2/Bax ratio was increased in group Dex.Compared with group I/R,apoptosis index and MDA content were significantly decreased,and SOD activity and Bcl-2/Bax ratio were increased in group Dex.Conclusion Dexmedetomidine can attenuate myocardial injury induced by renal I/R in rats,and the mechanism may be related to inhibited apoptosis in cardiomyocytes and reduced lipid peroxidation.