Objective To investigate the effect of dexmedetomidine (Dex)combined with ischemic preconditioning on liver ischemic reperfusion injury in rats in order to explore its possible mechanism. Methods Sixty healthy male SD rats weighing (251 ±18)g,were randomly (random number)divided into five groups (n =12 in each):sham-operation group (Group S:operation without ischemia), ischemia-reperfusion group (Group IR:hepatic pedicle occlusion for 30 min and reperfusion for 6 h), dexmedetomidine preconditioning group (Group Dex: dexmedetomidine 25 μg/kg was given intra-peritoneally at 30 min before operation),ischemic preconditioning group (Group IP:10 min ischemia,10 min reperfusion,followed by hepatic IR)and Dex combined with ischemic preconditioning group (Group Dex +IP:Dex 25μg/kg was given intra-peritoneally at 30 min befor operation,10 min ischemia and 10 min reperfusion was given followed by hepatic IR).The hepatic inflow of blood stream was occluded for 30 min by Pringle maneuver to establish hepatic ischemic reperfusion injury (HIRI)rat model.At the end of reperfusion for 6 h,the concentration of ALT,AST and LDH (lactate dehydrogenase)in serum were measured.The liver histological changes were examined after HE staining.The liver cell apoptosis were examined by TUNEL. The expression of heme oxygenase-1 were examined by Westeren blot and immunohistochemistry.H2 O2 and GSH (r-glutamylcysteinylglycine ) in liver tissue were detected by spectrophotometer.Differences among the groups were analyzed by one-way analysis of variance (ANOVA) and Student-Newman-Keul test by using SPSS version 17.0 software.Differences were considered significant at P <0.05.Results Serum concentrations of ALT,AST and LDH in group IR,Dex,IP and Dex +IP were significantly higher than those in group S (P =0.000).And those biomarkers in group Dex,IP and Dex +IP,were significantly lower than those in group IR (P =0.000).Furthermore,those biomarkers in group Dex +IP,were significantly lower than those in group Dex and IP (P =0.000).There were no significant difference in the serum concentrations of ALT and AST between group Dex and IP (P =0.550, 0.771),and the serum level of LDH in group Dex was significantly lower than that in group IP (P =0.000).The liver histopathological score and apoptosis index were the lowest in group S and the highest in group IR,and those in group Dex and group IP were significantly lower than those in group IR (P =0.000),and those in group Dex +IP were significantly lower than those in group Dex and group IP (P =0.000),and there were no significant difference between group Dex and IP (P =0.704,0.661 ).The expression score of HO-1 was the lowest in group S and the highest in group Dex +IP,and that in group Dex and group IP was significantly lower than that in group Dex +IP (P =0.000,0.002),and that in group IR was significantly lower than that in group Dex and group IP (P =0.000),and there was no significant difference between group Dex and IP (P =0.099).In respect of H2 O2 level and GSH level in liver tissue, compared with group S,the H2 O2 levels in groups IR,Dex,IP and Dex +IP were significantly higher (P=0.000,0.000,0.000,0.001)while the GSH levels were significantly lower (P =0.000).Compared with group IR,the H2 O2 level in group Dex,IP and Dex +IP was significantly lower than that in group IR while the GSH level was significantly higher (P =0.000 ).The H2 O2 level in group Dex +IP was significantly lower than that in group Dex and IP while the GSH level was significantly higher (P =0.000).There were no significant difference between group Dex and IP (P =0.480,0.667).Conclusions Both of dexmedetomidine and ischemic preconditioning can protect liver from ischemia reperfusion injury in rats to some extent,and the combined application of two gives better effects,which is attributed to the increasing expression of HO-1 to a certain extent.