Background Apurinic apyrimidinic endonuclease/redox effector factor 1 (APE1/Ref-1) is an important enzyme in the repair of reactive oxygen species-induced DNA damage,and its expression/activation can be induced by reactive oxygen species.The aim of this research was to investigate the relationship between multiple-organ injuries and expression of Ref-1 in the early period after liver transplantation.Methods One hundred and fifty adult male Wistar rats were divided randomly into three groups:liver transplantation,sham surgery,and untreated control.After liver transplantation,animals were sacrificed at different time points.Hepatic and renal functions were analyzed by serology.Histology,apoptotic levels,and Ref-1 expression were examined by immunohistochemistry in the liver,kidneys,intestines,and lungs.Results Serum levels of alanine aminotransferase and aspartate aminotransferase peaked 6 hours after liver transplantation and decreased appreciably after 12 hours in the transplantation group,suggesting that the degree of liver injury in the early period after transplantation peaked at 6 hours and then decreased.Pathological analyses showed that hepatic tissues were more severely injured in the transplantation group than in the sham and untreated groups.A considerable number of infiltrating inflammatory cells was observed around the portal vein in the transplantation group.Injuries to the kidneys,intestines,and lungs were milder after liver transplantation.Apoptotic levels increased after liver transplantation in all four organs examined.Ref-1 expression was higher in the transplantation group in the early period after liver transplantation than in the sham surgery and untreated control groups.Conclusion Ref-1 expression induced by ischemia-reperfusion injury may have a critical role in repairing multiple-organ injuries after liver transplantation.