title: Involvement of Na+-HCO3- cotransporter in mediating cyclic adenosine 3',5'-monophosphate-dependent HCO3- secretion by mouse endometrial epithelium.
abstract: The present study investigated the involvement of Na+-HCO3- cotransporter in mediating cAMP-stimulated HCO3- secretion across the cultured mouse endometrial epithelium using the short-circuit current (I(SC)) technique and intracellular pH measurement. Forskolin stimulated a rise in the I(SC), 55.6% and 52.1% of which could be reduced by the removal of extracellular Cl- or by eliminating the contribution of Cl- secretion by bumetanide, an inhibitor of Na+-K+-2Cl- cotransporter, respectively. More than 80% reduction in the forskolin-induced I(SC) was obtained when both Cl- and HCO3- in the bath were removed or in HCO3--free solution with bumetanide, indicating that the I(SC) depended on both Cl- and HCO3-. The presence of the Na+ channel-blocker amiloride in the apical solution did not reduce the forskolin-induced I(SC); however, the I(SC) could be abolished by removing Na+ from the bathing solution, suggesting that the Cl-- and HCO3--dependent I(SC) was also dependent on basolateral Na+. The forskolin-stimulated I(SC) could be reduced 43.6% by removal of HCO3- and 47.9% by a Na+-HCO3--cotransporter inhibitor, dihydrogen-4,4'-didsothiocyanostilbene-2,2'-disulfonic acid (H2DIDS). The inhibitory effect of H2DIDS was observed in Cl--free solution, but not when HCO3- was removed, thus confirming its effect on HCO3--dependent transport. Intracellular pH measurements demonstrated that the recovery from cellular acidification depended on the presence of both basolateral Na+ and HCO3-, further indicating the involvement of Na+-HCO3- cotransporter. Reverse transcription-polymerase chain reaction experiments confirmed the expression of Na+-HCO3- cotransporter in the mouse endometrium. The results suggest that basolaterally located Na+-HCO3- cotransporter is involved in mediating cAMP-stimulated HCO3- secretion across the mouse endometrial epithelium.
authors.affiliation: Epithelial Cell Biology Research Center, Faculty of Medicine, Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: X F
authors.initials: XF
authors.lastname: Wang
authors.forename: M K
authors.initials: MK
authors.lastname: Yu
authors.forename: K M
authors.initials: KM
authors.lastname: Leung
authors.forename: C Y
authors.initials: CY
authors.lastname: Yip
authors.forename: W H
authors.initials: WH
authors.lastname: Ko
authors.forename: C Q
authors.initials: CQ
authors.lastname: Liu
authors.forename: H C
authors.initials: HC
authors.lastname: Chan
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D004553:Electric Conductivity; D004717:Endometrium / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D005260:Female; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008813:Mice, Inbred ICR; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000494:pharmacology; D027982:Sodium-Bicarbonate Symporters / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D027982:Sodium-Bicarbonate Symporters; D005576:Colforsin; C018564:dihydro-DIDS; D012964:Sodium; D000242:Cyclic AMP; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid