ObjectiveTo investigate the effects of HO-1 on mast cells degranulation during liver ischemia/reperfusion injury.MethodsSD rats ( n =20) were randomly divided into 4 groups : ( 1 ) sham operation group, (2) ischemia/reperfusion injury group (I/RI group), (3) CoPP group, CoPP was given before 24 h(5 mg/kg), (4) ZnPP group, ZnPP was given before 24 h (20 mg/kg). The rat model of liver ischemia/reperfusion was built. Samples were collected after 2 hours reperfusion. HO-1 mRNA expression was assessed by RT-PCR. The expression of HO-1 protein was assessed by Western blot. Serum ALT, AST levels were determined. The amount of degranulated mast cells were detected by toluidine blue staining. Liver injuries were evaluated by HE staining.ResultsCompared to sham group, liver HO-1mRNA and protein expression, ALT, AST levels, the number of degranulated mast cells significantly increased in I/RI group, CoPP group and ZnPP group. Moreover, liver injuries were more serious. Compared to I/RI group, there were increased HO-1mRNA and protein expression, reduced ALT, AST levels and the number of degranulated mast cells, also reduced liver injuries were found in CoPP group. Compared to I/RI group, the expression of HO-ImRNA and protein was down-regulated, ALT, AST levels elevated and the number of degranulatedmastcellsincreasedaccompanyingmoreseriousliverinjuriesinZnPPgroup.ConclusionsHO-1 overexpression reduces liver ischemia/reperfusion injury, possibly by inhibiting mast cells degranulation in liver tissues.