Regional differences in the cellular proliferation activity of the regenerating rat pancreas after partial pancreatectomy

The proliferation activity of component cells and its regional differences in the regenerating rat pancreas after 90% pancreatectomy were examined by bromodeoxyuridine (BrdU) immunohistochemistry. Cells of the ductal system a nd the centroacinar cells showed a rapid increase in labeling indices at da y 2 after pancreatectomy, followed by a second peak of a mild increase at d ays 5 to 7. No regional difference in the labeling index was recognized in the ductal elements. In contrast, the labeling index of acinar cells starte d to increase at day 3, reaching a definite peak at day 5. Furthermore, aci nar cells in the region close to the duodenum had labeling indices more tha n 2 times higher than those in the portions further away from the duodenum, Acinar cells increased in number as early as from day 3 after surgery. The se result suggested that the parental cells of regeneration were located in the ductal epithelium. It is highly probable that the proliferation of aci nar cells is controlled by some unknown trophic factor(s) which is released locally from the duodenum, but does not involve a neural or a circulatory route. The phenomenon may be closely linked to the known fact that the inci dence of pancreatic cancer is highest in the head region.