P2Y(11), a purinergic receptor acting via cAMP, mediates secretion by pancreatic duct epithelial cells

Pancreatic duct epithelial cells (PDEC) mediate the exocrine secretion of f luid and electrolytes. We previously reported that ATP and UTP interact wit h P2Y(2) receptors on nontransformed canine PDEC to increase intracellular free Ca2+ concentration ([Ca2+](i)) and stimulate Ca2+-activated Cl- and K channels. We now report that ATP interacts with additional purinergic rece ptors to increase cAMP and activate Cl- channels. ATP, 2- methylthio-ATP, a nd ATP-gamma -S stimulated a 4- to 10-fold cAMP increase with EC50 of 10-10 0 muM. Neither UTP nor adenosine stimulated a cAMP increase, excluding a ro le for P2Y(2) or P-1 receptors. Although UTP stimulated an I-125(-) efflux that was fully inhibited by 1,2-bis(2-aminophenoxy) ethane-N,N,N',N/-tetraa cetic acid tetra( acetoxymethyl) ester (BAPTA-AM), ATP stimulated a partial ly resistant efflux, suggesting activation of additional Cl- conductances t hrough P2Y(2)-independent and Ca2+-independent pathways. In Ussing chambers , increased cAMP stimulated a much larger short-circuit current (I-sc) incr ease from basolaterally permeabilized PDEC monolayers than increased [Ca2+] (i). Luminal ATP and UTP and serosal UTP stimulated a small Ca2+-type I-sc increase, whereas serosal ATP stimulated a large cAMP-type I-sc response. S erosal ATP effect was inhibited by P2 receptor blockers and unaffected by B APTA-AM, supporting ATP activation of Cl- conductances through P2 receptors and a Ca2+-independent pathway. RT-PCR confirmed the presence of P2Y(11) r eceptor mRNA, the only P2Y receptor acting via cAMP.