title: Phosphatidylinositol 3-kinase is involved in prostaglandin E2-mediated murine duodenal bicarbonate secretion.
abstract: Prostaglandin E(2) (PGE(2)) plays an important role in the regulation of duodenal bicarbonate (HCO(3)(-)) secretion, but its signaling pathway(s) are not fully understood. In the present study, we investigated the signaling pathways involved in PGE(2)-mediated duodenal HCO(3)(-) secretion. Murine duodenal mucosal HCO(3)(-) secretion was examined in vitro in Ussing chambers by pH-stat titration in the presence of a variety of signal transduction modulators. Phosphatidylinositol 3-kinase (PI3K) activity was measured by immunoprecipitation of PI3K and ELISA, and Akt phosphorylation was measured by Western analysis with anti-phospho-Akt and anti-Akt antibodies. PGE(2)-stimulated duodenal HCO(3)(-) secretion was reduced by the cAMP-dependent signaling pathway inhibitors MDL-12330A and KT-5720 by 23% and 20%, respectively; the Ca(2+)-influx inhibitor verapamil by 26%; and the calmodulin antagonist W-13 by 24%; whereas the PI3K inhibitors wortmannin and LY-294002 reduced PGE(2)-stimulated HCO(3)(-) secretion by 51% and 47%, respectively. Neither the MAPK inhibitor PD-98059 nor the tyrosine kinase inhibitor genistein altered PGE(2)-stimulated HCO(3)(-) secretion. PGE(2) application caused a rapid and concentration-dependent increase in duodenal mucosal PI3K activity and Akt phosphorylation. These results demonstrated that PGE(2) activates PI3K in duodenal mucosa and stimulates duodenal HCO(3)(-) secretion via cAMP-, Ca(2+)-, and PI3K-dependent signaling pathways.
authors.affiliation: Department of Gastroenterology, Hepatology, and Endocrinology, Hannover Medical School, Carl-Neuberg Strasse 1, 30625 Hannover, Germany.
authors.forename: Bi-Guang
authors.initials: BG
authors.lastname: Tuo
authors.forename: Guo-Rong
authors.initials: GR
authors.lastname: Wen
authors.forename: Ursula
authors.initials: U
authors.lastname: Seidler
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002227:Carbazoles / Q000494:pharmacology; D002867:Chromones / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D015232:Dinoprostone / Q000494:pharmacology / Q000502:physiology*; D004386:Duodenum / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D007097:Imines / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000378:metabolism; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D001639:Bicarbonates; D002227:Carbazoles; D002867:Chromones; D005419:Flavonoids; D007097:Imines; D007211:Indoles; D009025:Morpholines; D011758:Pyrroles; D013449:Sulfonamides; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C057416:KT 5720; C033772:N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide; C014925:RMI 12330A; D014700:Verapamil; D019833:Genistein; D000242:Cyclic AMP; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020929:Mitogen-Activated Protein Kinase Kinases; D015232:Dinoprostone; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D000077191:Wortmannin