Site-specific distribution of phospholipase D isoforms in the rat pancreas

Phospholipase D (PLD), one of the signal transducing enzymes, is recognized to play a role in the pancreatic exocrine and endocrine secretion, and yet the distribution of PLD in the pancreas has remained unclarified. We investigated the expression and localization of PLD isoforms, PLD1 and PLD2, in the rat pancreas. Western blot analysis showed that PLD1-immunoreactive band was observed in the islets, but not in the acinar cells. In contrast, PLD2-immunoreactive band was observed in both the islets and the acinar cells. In the immunohistochemistry, PLD1 was evenly distributed throughout the islets while PLD2 immunoreactivity was more intense in the periphery than in the central portion of the islets. To further elucidate the cell-specific localization of PLD2 in the islets, double immunofluorescent staining was performed. PLD2 was mainly localized in A and PP cells, which secrete glucagon and pancreatic polypeptide, respectively. PLD2 was also detected in acinar cells, ductal epithelial cells and intrapancreatic nerve fibers. Meanwhile, PLD1 was detected in ductal epithelial cells and intrapancreatic ganglia, but not in acinar cells. On the basis of this heterogeneity in the distribution of PLD isoforms, it is suggested that PLD might play a specific role in the pancreatic exocrine and endocrine function.