| Background and Aim China is one of the areas that have high incidences of liver diseases in the world, especially malignant tumor of liver and virus hepatitis, which are severely threatening people's health. After 1980s, there was a great development in liver transplantation. With the improvement of surgical technic of organ preservation, level of treatment to the period of surrounding operation and effect of immunodepressant, liver transplantation has become an effective therapy for many chronic, progressing or irreversible liver diseases. However, the occurrence of complications, such as liver function failure, renal failure, rejection, stegnosis of biliary tract, thrombus, and recurrence of tumor, is puzzling medical workers all the time, So, medical scientists spared no effort to explore various methods to keep liver graft in good function status. The unavoidable ischemical reperfusion injury of liver transplantation is one of the most important factors that can induce poor early graft function(PEGF) and even primary nonfunction(PNF). The large amount of vasoactive substances released after reperfusion can influence the microcirculation of graft, and then make liver graft vulnerable to PNF. So, the ischemical reperfusion injury of liver transplantation has drawn more attentionthan ever before. The pathophysiologic mechanisms of liver ischemical reperfusion injury are complicated, including synthesis and releasing of cytokines, gathering and infiltrating of neutrophils, releasing of oxygen free radicals, disorder of energy metabolism, etc. Apoptosis is so called programmed cell death controlled by genes. It has a distinctive pattern of manifestation, and many factors participate in its occurrence and development. In the past few years, the important role of apoptosis in liver transplantation has gradually drawn medical scientists' attention. Medical researchers found that apoptosis was one of the most important manifestations of early hepatocytes injury after liver transplantation, and it was also a significant factor that can influence the function of liver graft. Through making liver graft tolerant to ischemia, the protective effects of ischemic preconditioning on ischemical reperfusion injury have been proved in many organs, animal models and even clinic. However, because most of liver grafts are got from brain death donators, the application of ischemical preconditioning to liver transplantation is limited. So, people make great efforts to find other effective methods to protect liver graft. In some investigations, scientists found that ischemic postconditioning and preconditioning had similar protective effects. They thought ischemic postconditioning could relieve ventricular fibrillation and lessen infarct size of cardiac muscles. But until now, there is little research of the effect of ischemic postconditioning on liver transplantation. In this study, through establishing liver transplantation model of rats with same strain, we investigated the protective effects of ischemic postconditioning on ischemical reperfusion injury and apoptosis of liver grafts and its possible mechanisms.Method 48 male SD rats, weighing 280-320g, were randomly divided into two groups. In each group, there were 12 donators and recipients respectively, the weight of donators were lighter than recipients'. The method of twosleeves anastomoses for rat liver transplantation was performed. The average cold preservation time of donor liver was 100 minutes, and the anhepatic phase was limited within 21 minutes. (Dcontrol group(control): there was no intervention on donor livers either before harvested or after implanted;? ischemic postconditioning group (Post-con): immediately after donor liver was implanted, just before the onset of reperfusion, several brief reperfusion-ischemia were given before persistent reperfusion. Half of each group(n=6) were used to take blood sample and hepatic tissue after 2 hours of reperfusion to detect the levels of AST\ ALI\ LDH^ TNF— a ? NE in serum and the contents of GSH—PX, MDA^ MPCK SOD in liver. The other half of each group was used to take sample of liver tissue after 6 hours of reperfusion. The apoptotic hepatocytes were confirmed by transmission electron microscope and counted with in situ nick end labeling(TUNEL) method and light microscopy. The expression of caspase-3 gene protein was studied by immunohistochemical staining and the quantitatively examined by image analysis system.Results The level of serum ALT in Post-con group(595.500±445.503 IU/L) was significantly lower than in control group(1075.167 ± 193.150 IU/L)(P<0.05), the level of serum AST in Post-con group(709.000± 256.055 IU/L) was significantly lower than in control group(1479.000 ± 392.094 IU/L)(P<0.01), the level of serum LDH in Post-con group(1354.667 ± 292.579 IU/L) was significantly lower than in control group(2410.000 + 870.647 IU/L)(P<0.05). The content of liver tissue MDA in Post-con group(0.554±0.116 nmol/mgprot) was significantly lower than in control group(0.816±0.105nmol/mgprot)(P<0.01), liver tissue GSH—PX activity in Post-con group(88.072± 15.997 U/gprot) was significantly higher than in control group(59.440 ± 4.488 U/gprot)(P<0.01), liver tissue MPO activity in...
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