Early expression of adenosine 5'-triphosphate-gated P2X7 receptors in the developing rat pancreas

Objectives: Extracellular adenosine 5'-triphosphate modulates the functions of the adult pancreas via 2 nucleotide receptor families, the P2X and P2Y receptors. Expression of the P2X(7) receptor has been demonstrated in islet cells of the pancreas, particularly the mature alpha cells that secrete glucagon. In the streptozotocin-induced diabetic model, a loss of insulin-secreting cells was accompanied by an increase in a cells that expressed the P2X(7) receptor. Methods: In the present study, we have examined the expression of P2X(7) receptors in the developing pancreas from embryonic days 10 (E10) to E18. Results: We detected P2X(7) receptor-immunoreactive cells in pancreatic islet cells as early as E11' before glucagon expression. Subsequently, P2X(7) receptors were expressed in glucagon-secreting cells at E12, and complete colocalization was observed at E14. Occasional colocalization of P2X(7) receptors and insulin was observed in scattered cells at E12 and E14, but not at E18, when the glucagon- and insulin-secreting cells were almost completely segregated. Conclusions: It was found that P2X(7) receptors were expressed early in a subpopulation of glucagon- and insulin-immunopositive cells in developing islets and subsequently became restricted to glucagon-expressing cells as development proceeded. The possible functional significance of these changes is discussed.