P2Y receptors mediate Ca2+ signaling in duodenocytes and contribute to duodenal mucosal bicarbonate secretion.
Since little is known about the role of P2Y receptors (purinoceptors) in duodenal mucosal bicarbonate secretion (DMBS), we sought to investigate the expression and function of these receptors in duodenal epithelium. Expression of P2Y(2) receptors was detected by RT-PCR in mouse duodenal epithelium and SCBN cells, a duodenal epithelial cell line. UTP, a P2Y(2)-receptor agonist, but not ADP (10 microM), significantly induced murine duodenal short-circuit current and DMBS in vitro; these responses were abolished by suramin (300 microM), a P2Y-receptor antagonist, or 2-aminoethoxydiphenyl borate (2-APB; 100 microM), a store-operated channel blocker. Mucosal or serosal addition of UTP induced a comparable DMBS in wild-type mice, but markedly impaired response occurred in P2Y(2) knockout mice. Acid-stimulated DMBS in vivo was significantly inhibited by suramin (1 mM) or PPADS (30 microM). Both ATP and UTP, but not ADP (1 microM), raised cytoplasmic-free Ca(2+) concentrations ([Ca(2+)](cyt)) with similar potencies in SCBN cells. ATP-induced [Ca(2+)](cyt) was attenuated by U-73122 (10 microM), La(3+) (30 microM), or 2-APB (10 microM), but was not significantly affected by nifedipine (10 microM). UTP (1 microM) induced a [Ca(2+)](cyt) transient in Ca(2+)-free solutions, and restoration of external Ca(2+) (2 mM) raised [Ca(2+)](cyt) due to capacitative Ca(2+) entry. La(3+) (30 microM), SK&F96365 (30 microM), and 2-APB (10 microM) inhibited UTP-induced Ca(2+) entry by 92, 87, and 94%, respectively. Taken together, our results imply that activation of P2Y(2) receptors enhances DMBS via elevation of [Ca(2+)](cyt) that likely results from an initial increase in intracellular Ca(2+) release followed by extracellular Ca(2+) entry via store-operated channel.
Dong
Xiao
X
Department of Medicine, University of California, La Jolla, CA 92093, USA.
Smoll
Eric James
EJ
Ko
Kwang Hyun
KH
Lee
Jonathan
J
Chow
Jimmy Yip
JY
Kim
Ho Dong
HD
Insel
Paul A
PA
Dong
Hui
H
D000244:Adenosine Diphosphate / Q000378:metabolism; D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001896:Boron Compounds / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D004285:Dogs; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D004963:Estrenes / Q000494:pharmacology; D005260:Female; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D007419:Intestinal Secretions / Q000378:metabolism*; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009543:Nifedipine / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D018048:Receptors, Purinergic P2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D058473:Receptors, Purinergic P2Y2; D013498:Suramin / Q000494:pharmacology; D013997:Time Factors; D014544:Uridine Triphosphate / Q000378:metabolism
D000634:Aminoquinolines; D001639:Bicarbonates; D001896:Boron Compounds; D002121:Calcium Channel Blockers; D004963:Estrenes; C546386:P2ry2 protein, mouse; D058919:Purinergic P2 Receptor Antagonists; D011760:Pyrrolidinones; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C069657:1-(2-methylphenyl)-4-methylamino-6-methyl-2,3-dihydropyrrolo(3,2-c)quinoline; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; D000244:Adenosine Diphosphate; C109986:2-aminoethoxydiphenyl borate; D009543:Nifedipine; D014544:Uridine Triphosphate