title: Participation of prostaglandin E receptor EP4 subtype in duodenal bicarbonate secretion in rats.
abstract: We examined, by using a specific PGE receptor subtype EP4 agonist and antagonist, the involvement of EP4 receptors in duodenal HCO(3)(-) secretion induced by PGE(2) and mucosal acidification in rats. Mucosal acidification was achieved by exposing a duodenal loop to 10 mM HCl for 10 min, and various EP agonists were given intravenously 10 min before the acidification. Secretion of HCO(3)(-) was dose-dependently stimulated by AE1-329 (EP4 agonist), the maximal response being equivalent to that induced by sulprostone (EP1/EP3 agonist) or PGE(2). The stimulatory action of AE1-329 and PGE(2) but not sulprostone was attenuated by AE3-208, a specific EP4 antagonist. This antagonist also significantly mitigated the acid-induced HCO(3)(-) secretion. Coadministration of sulprostone and AE1-329 caused a greater secretory response than either agent alone. IBMX potentiated the stimulatory action of both sulprostone and AE1-329, whereas verapamil mitigated the effect of sulprostone but not AE1-329. Chemical ablation of capsaicin-sensitive afferent neurons did not affect the response to any of the EP agonists used. We conclude that EP4 receptors are involved in the duodenal HCO(3)(-) response induced by PGE(2) or acidification in addition to EP3 receptors. The process by which HCO(3)(-) is secreted through these receptors differs regarding second-messenger coupling. Stimulation through EP4 receptors is mediated by cAMP, whereas that through EP3 receptors is regulated by both cAMP and Ca(2+); yet there is cooperation between the actions mediated by these two receptors. The neuronal reflex pathway is not involved in stimulatory actions of these prostanoids.
authors.affiliation: Dept. of Pharmacology and Experimental Therapeutics, Kyoto Pharmaceutical University, Misasagi, Yamashina, Kyoto 607-8414, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Aoi
authors.forename: Eitaro
authors.initials: E
authors.lastname: Aihara
authors.forename: Masato
authors.initials: M
authors.lastname: Nakashima
authors.forename: Koji
authors.initials: K
authors.lastname: Takeuchi
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology; D015232:Dinoprostone / Q000031:analogs & derivatives* / Q000494:pharmacology; D004338:Drug Combinations; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism*; D006851:Hydrochloric Acid / Q000494:pharmacology; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010654:Phenylbutyrates / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018078:Receptors, Prostaglandin E / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D058309:Receptors, Prostaglandin E, EP4 Subtype; D014700:Verapamil / Q000494:pharmacology
chemical_list: C487890:4-(4-cyano-2-(2-(4-fluoronaphthalen-1-yl)propionylamino)phenyl)butyric acid; D001639:Bicarbonates; D004338:Drug Combinations; D008738:Methyl Ethers; D009281:Naphthalenes; C461399:ONO-AE1-329; D010654:Phenylbutyrates; D018078:Receptors, Prostaglandin E; D058309:Receptors, Prostaglandin E, EP4 Subtype; C016767:sulprostone; D014700:Verapamil; D015232:Dinoprostone; D006851:Hydrochloric Acid; D002211:Capsaicin; D015056:1-Methyl-3-isobutylxanthine