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

Abstract

In view of the evidence for a role for extracellular ATP in both pancreatic endocrine and exocrine functions, we have investigated the expression of P2X and P2Y receptors in this tissue in neonate and aged rat and mouse. Using immunohistochemistry it was shown that P2X₁, P2X₄, P2X₇, P2Y₁ and P2Y₂ receptors were present in different regions of the rat and mouse pancreas; P2X₃ and P2X₆ receptors were not found, and P2X₅ immunolabelling was only found in some nerves. The pancreatic vasculature of both rat and mouse expressed P2X₁, P2X₂, P2Y₁ and P2Y₂ 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 pancreas, while there was no P2Y₁ expression in aged rat pancreas. P2X₇ receptors had a consistent pattern of distribution in all of the groups examined, being located in the outer periphery of the islet. Using antibodies raised against insulin, somatostatin and glucagon, double-labelling immunofluorescence was used to identify P2X₇-positive cells in different islet of Langerhans cell populations. Our results demonstrated a clear immunoreaction to P2X₇ receptors in islet α cells, while no P2X₇ was expressed in β and δ cells. The significance of the differential expression of P2 receptors in the pancreas during development and ageing, and a possible role for the proliferation and death of the islet cell population are discussed.