title: Electroneutral secretion of bicarbonate by guinea pig gallbladder epithelium.
abstract: Transepithelial HCO3- movement in guinea pig gallbladder was investigated in vitro. Absorptive (JHCO3ms) and secretory (JHCO3sm) HCO3- fluxes, determined by use of the pH-stat method were approximately 1.0 and 2.1 mumol X cm-2 X h-1, respectively. The resultant net secretion equaled in magnitude, and balanced electrically, the excess in net absorption of Cl- over that of Na+ X JHCO3sm was dependent on luminal Cl- and serosal Na+; it was inhibited by mucosal 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS; 10(-3) M) and serosal ouabain (3 X 10(-5) M) but not by serosal amiloride (10(-3) M) and scarcely by bilateral methazolamide (10(-4) M). JHCO3ms was reduced by mucosal Cl- but enhanced by serosal Cl-; it was dependent on mucosal Na+ and inhibited by mucosal amiloride and bilateral methazolamide. Our findings are consistent with a model in which 1) serosal HCO3- enters the cell in cotransport with Na+ and is then extruded into the lumen by Cl-(-)HCO3- exchange at the apical membrane; 2) mucosal HCO3- enters the cell secondary to apical membrane Na+-H+ exchange and recycles into the lumen via Cl-(-)HCO3- exchange or is, to a lesser extent, absorbed across the basolateral membrane.
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000042:Absorption; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D006168:Guinea Pigs; D008297:Male; D009092:Mucous Membrane / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D012704:Serous Membrane / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D001743:Urinary Bladder / Q000166:cytology / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D002257:Carbonic Anhydrase Inhibitors; D002712:Chlorides; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D010042:Ouabain; D012964:Sodium