Changes in expression of P2 receptors in rat and mouse pancreas during development and ageing

In view of the evidence for a role for extracellular ATP in both pancreatic endocrine and exocrine functions, we have investigated the expression of P 2X and P2Y receptors in this tissue in neonate and aged rat and mouse. Usin g immunohistochemistry it was shown that P2X(1), P2X(4), P2X(7), P2Y(1) and P2Y, receptors were present in different regions of the rat and mouse panc reas; P2X(3) and P2X(6) receptors were not found, and P2X(5) immunolabellin g was only found in some nerves. The pancreatic vasculature of both rat and mouse expressed P2X1, P2X,, P2Y, and P2Y,, receptors in the smooth muscle. P2X1 and P2X4 receptors were absent in the islets of the neonate pancreas, but were progressively upregulated with age after birth. In contrast, the greatest expression of P2Y1 in cells from the duct system was in neonate pa ncreas, while there was no P2Y, expression in aged rat pancreas. P2X7 recep tors had a consistent pattern of distribution in all of the groups examined , being located in the outer periphery of the islet. Using antibodies raise d against insulin, somatostatin and glucagon, double-labelling immunofluore scence was used to identify P2X(7)-positive cells in different islet of Lan gerhans cell populations. Our results demonstrated a clear immunoreaction t o P2X7 receptors in islet alpha cells, while no P2X7 was expressed in beta and delta cells. The significance of the differential expression of P2 rece ptors in the pancreas during development and ageing, and a possible role fo r the proliferation and death of the islet cell population are discussed.