Abstract： Background Little is known of the effects of hydrocortisone on cell adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and its counterreceptors (LFA-1, Mac-1) in acute pancreatitis (AP). We investigated the effects of prior treatment with hydrocortisone on the production of ICAM-1 and its counterreceptors (LFA-1 and Mac-1) in AP of rats to clarify the effect of hydrocortisone on induced acute pancreatitis.Methods Acute pancreatitis was induced by infusion of 5% chenodeoxycholic acid into the pancreatic duct, followed by ligation of pancreatic duct. Before induction of acute pancreatitis, rats were treated with hydrocortisone (n=20) or 0.9%saline (n=20). Blood and specimens from pancreas and lung were obtained from 5 rats from each treatment euthanized at 1 hour or 3 hours, 6 hours, 12 hours. Expression of ICAM-1 was assessed by immunohistochemistry and Western blot analysis of pancreas and lungs. The expression of LFA-1 and Mac-1 on neutrophils was detected by flow cytometer.The therapeutic effect of hydrocortisone was assessed from injuries to pancreas and lung.Results ICAM-1 expression in the pancreas of hydrocortisone group was significantly less than in control group at 3 hours and 6 hours. In the lungs of hydrocortisone group, ICAM-1 expression was significantly less than in control group at 3 hours, 6 hours and 12 hours. The expression of LFA-1 and Mac-1 on neutrophils in blood increased significantly in control group over hydrocortisone group. Increased expression of ICAM-1, LFA-1 and Mac-1 preceded leukocyte infiltration. Compared to untreated animals with acute pancreatitis, rats pretreated with hydrocortisone had significantly reduced histological lung injury and output of ascitic fluid.Conclusions Prior treatment with hydrocortisone before the induction of acute pancreatitis ameliorates pulmonary injury and the output of ascitic fluid and reduces the expression of ICAM-1 and its counterreceptors (LFA-1, Mac-1) in acute pancreatitis.