AIM: Pancreatic regenerating protein (regⅠ) stimulates pancreatic regeneration after pancreatectomy and is mitogenic to ductal andβ-cells. This suggests that regⅠand its receptor may play a role in recovery after pancreatic injury. We hypothesized that regⅠand its receptor are induced in acute pancreatitis. METHODS: Acute pancreatitis was induced in male Wistar rats by retrograde injection of 3% sodium taurocholate into the pancreatic duct. Pancreata and serum were collected 12, 24, and 36 hours after injection and from normal controls (4 rats/group). RegⅠreceptor mRNA, serum regⅠprotein, and tissue regⅠprotein levels were determined by Northern analysis, enzyme-linked immunosorbent assay (ELISA), and Western analysis, respectively. Immunohistochemistry was used to localize changes in regⅠand its receptor. RESULTS: Serum amylase levels and histology confirmed necrotizing pancreatitis in taurocholate treated rats. There was no statistically significant change in serum regⅠconcentrations from controls. However, Western blot demonstrated increased tissue levels of regⅠat 24 and 36 h. This increase was localized primarily to the acinar cells and the ductal cells by immunohistochemistry. Northern blot demonstrated a significant increase in regⅠreceptor mRNA expression with pancreatitis. Immunohistochemistry localized this increase to the ductal cells, islets, and acinar cells. CONCLUSION: Acute pancreatitis results in increased tissue regⅠprotein levels localized to the acinar and ductal cells, and a parallel threefold induction of regⅠreceptor in the ductal cells, islets, and acinar cells. These changes suggest that induction of reg I and its receptor may be important for recovery from acute pancreatitis. AIM: Pancreatic regenerating protein (reg I) stimulates pancreatic regeneration after pancreatectomy and is mitogenic to ductal and beta-cells. This suggests that reg I and its receptor may play a role in recovery after pancreatic injury. We hypothesized that reg I and its receptors are induced in acute pancreatitis. METHODS: Acute pancreatitis was induced in male Wistar rats by retrograde injection of 3% sodium taurocholate into the pancreatic duct. Pancreata and serum were collected 12, 24, and 36 hours after injection and from normal controls (4 rats / group) , serum regⅠprotein, and tissue regⅠprotein levels were determined by Northern analysis, enzyme-linked immunosorbent assay (ELISA), and Western analysis, respectively. Immunohistochemistry was used to localize changes in reg Ⅰ and its receptor. RESULTS: Serum amylase levels and histology confirmed necrotizing pancreatitis in taurocholate treated rats. There was no significant significant change in serum reg However, Western blot demonstrated increased tissue levels of regⅠat 24 and 36 h. This increase was localized to the acinar cells and the ductal cells by immunohistochemistry. Northern blot demonstrated a significant increase in reg I receptor mRNA expression with pancreatitis. Immunohistochemistry localized this increase to the ductal cells, islets, and acinar cells. CONCLUSION: Acute pancreatitis results in increased tissue regⅠprotein levels localized to the acinar and ductal cells, and a parallel threefold induction of regⅠreceptor in the ductal cells, islets, and acinar cells. These changes suggest that induction of reg I and its receptor may be important for recovery from acute pancreatitis.