Clin Transplantation 1999: 13: 76–82 Printed in Ireland. All rights resered Role of P-selectin expression in hepatic ischemia and reperfusion injury Singh I, Zibari GB, Brown MF, Granger DN, Eppihimer M, Zizzi H, Cruz L, Meyer K, Gonzales E, McDonald JC. Role of P-selectin ex- pression in hepatic ischemia and reperfusion injury. Clin Transplantation 1999: 13: 76 – 82. © Munksgaard, 1999 Abstract: Background. Researchers have shown that reperfusion of is- chemic tissues initiates a complex series of reactions that paradoxically injure tissues. Although several mechanisms have been proposed to ex- plain the pathobiology of ischemic/reperfusion (I/R) injury, much at- tention has focused on adhesion molecules. Our research is intended to show the kinetics of P-selectin in the liver in response to I/R injury. Methods. Left-lobar hepatic ischemia was induced for 30 min in 35 C57BL-6 mice and 20 P-selectin-deficient (K-O) mice. P-selectin expres- sion was measured in these mice at 20 min, 2, 5, 12 and 24 h reperfu- sion times, as well as in control and sham animals. The animals were injected with radio-labeled P-selectin monoclonal antibody and the or- gans were harvested for counts/g tissue, expressed as the percentage injected dose. Serum liver enzymes were measured and pathological sections of ischemic and control livers were performed. The unpaired t -test was used for statistical analysis. Results. P-selectin expression showed two peaks in this animal model. The first peak was at 20 min and the second peak at 5 h of reperfusion (p 0.001). We documented an 8-fold increase in aspartate aminotrans- ferase (AST), alanine aminotransferase (ALT) and lactate dehydroge- nase (LDH) levels 10 h following I/R injury. Pathological specimens showed periportal necrosis consistent with an ischemic event. P-selectin K-O mice showed no up-regulation as a separate control group, and the liver enzymes were significantly lower than the wild-type mice at 10 h (p 0.001). Conclusion. P-selectin has a bimodal expression following hepatic I/R injury. The first peak is attributed to the Weibel–Palade bodies and the second to new translational P-selectin. We noted no difference in the up-regulation of P-selectin in the ischemic and non-ischemic liver lobes in the same animal. I Singh a , GB Zibari a , MF Brown a , DN Granger b , M Eppihimer b , H Zizzi a , L Cruz c , K Meyer a , E Gonzales c and JC McDonald a a Departments of Surgery, b Physiology and c Pathology, Louisiana State University Medical Center, Shreveport, Louisiana, USA Key words: ischemia/reperfusion – P-selectin – transgenic mice Corresponding author: GB Zibari, MD, FACS, Division of Transplantation, Depart- ment of Surgery, Louisiana State University Medical Center, 1501 Kings Highway, Shreveport, LA 71130, USA Early restitution of blood flow to ischemic tissue is essential to halt the progression of cellular injury associated with decreased oxygen and nutrient de- livery. Recognition of this fact provides the basis for the traditional view that minimizing ischemic time is the only important intervention for dimin- ishing the extent of ischemic injury. However, re- cent studies have shown that reperfusion of ischemic tissues initiates a complex series of reac- tions that paradoxically injures tissues (1 – 3). Al- though several mechanisms have been proposed to explain the pathobiology of ischemic/reperfusion (I/R) injury, most attention has focused on the role of reactive oxygen metabolites and inflammatory leukocytes. The I/R injury has been associated with multiple factors including enhanced produc- tion of inflammatory mediators, increased rolling, adherence and emigration of leukocytes, and pro- tein leakage in the post-capillary venules (17 – 19, 21, 25). There is a substantial body of evidence that leukocyte – endothelial cell adhesion is impor- tant for the microvascular dysfunction induced by I/R (2–4, 22–24, 26). This work has led to the proposal that free radical ablation or inhibition of post-ischemic neutrophil infiltration may prove useful in treating I/R injury. A simple mechanism 76