Quantification of P-selectin expression after renal ischemia and reperfusion

Neutrophils are important in ischemia and reperfusion injury. Multiple factors may be responsible for the adhesion of granulocytes to endothelial cells. P-selectin is a carbohydrate-binding glycoprotein that is stored preformed in endothelial cells as Weibel-Palade bodies. This preformation implies a very early role of P-selectin in the leukocyte adhesion process. Previous studies of P-selectin have not quantified its expression. The purpose of this study is to quantitate the expression and time course of P-selectin in response to renal ischemia and reperfusion injury. P-selectin was measured in 34 C57BL-6 mice after 30 minutes of occlusive left renal ischemia followed by 20 minutes, 2, 5, 10, and 24 hours of reperfusion. This was also performed in control and sham laparotomy groups. P-selectin was quantified using a new double radiolabeled 125I/131I monoclonal antibody technique and reported as percent injected dose per gram of tissue. P-selectin expression peaked at 20 minutes, plateaued up to 5 hours, and fell at 10 hours. Additionally, genetically altered mice that do not express P-selectin showed no up regulation after 5 hours of reperfusion. Pathology results confirmed significant renal injury. Renal ischemia and reperfusion injury caused significant upregulation of P-selectin. Expression of P-selectin at the short reperfusion time of 20 minutes reinforces the premise that P-selectin is one of the earliest adhesion molecules expressed. This early peak is probably caused by the release of preformed P-selectin. The delineation of these mechanisms of injury may be important in understanding and preventing renal injury in transplantation, sepsis, and shock.