Objective:To observe the expression of local angiotensin-converting enzyme 2 (ACE-2) in rat liver and its relationship with preservation injury (PI) after transplantation,so as to determine the possible role of local renin-angiotensin system (RAS) in PI caused by the cold-preservation in liver transplantation.Methods:The donor liver grafts were divided into cold preservation (CP) and non-cold preservation (NCP) groups;we also included a sham operation group without transplantation.The mRNA and protein levels of ACE-2 in the transplanted livers were detected by quantitative real-time PCR and Western blotting assay,respectively.The location of ACE-2 protein and pimonidazole in liver was detected by immunohistochemistry.Furthermore,histological evaluation was applied to verify the extent of liver damage.Results:Histological injuries of different degrees existed after liver transplantation; the injury was more obvious in the CP group.Compared with the sham operation group,the mRNA and protein expression of ACE-2 was significantly increased after liver transplantation (P<0.05 or P<0.01),and the expression of the CP group was significantly higher than that of the NCP group (P<0.05).Pimonidazole staining was positive around the hepatic veins in the transplantation groups,and the intensity of staining was positively correlated with the expression of ACE-2 mRNA (r=0.78,P<0.001).Conclusion:It is indicated that ACE-2 expression is closely associated with tissue hypoxia during cold preservation-induced PI ,and local RAS may play an important role in PI during liver transplantation.