title: The role of the basolateral outwardly rectifying chloride channel in human airway epithelial anion secretion.
abstract: The purpose of this study was to characterize basolateral anion channels in Calu-3 and normal human bronchial epithelial cells, and their role in anion secretion. Patch clamp studies identified an outwardly rectifying Cl- channel (ORCC), which could be activated by the adenosine receptor agonist 5'-(N-ethylcarboxamido)adenosine (NECA). Short-circuit current measurements revealed that NECA activates a basolateral, but not an apical, anion conductance sensitive to 4,4'-diisothiocyanatostilbene-2, 2'-disulfonic acid, and to 9-anthracenecarboxylic acid, but not to 4,4'-dinitrostilbene-2,2'-disulfonic acid. Apical membrane permeabilization studies confirmed the presence of basolateral anion channels, established their halide permeability sequence (Cl- >/= Br- >> I-), and demonstrated their outwardly rectifying nature. Experiments using H-89, forskolin, and Ht31 demonstrated that adenosine receptor dependent activation of basolateral ORCC was cAMP- and potentially A-kinase anchoring protein-dependent. Neither BAPTA-AM treatment nor basolateral Ca2+ removal had any effect on the activation of these channels. Anion replacement and 36Cl- flux studies show that Calu-3 cells primarily secrete HCO3- when stimulated with NECA, and that Cl- secretion can be stimulated by blocking basolateral ORCC, whereas normal human bronchial epithelial cells exclusively secrete Cl- under all conditions studied. We propose a novel model of anion secretion in which ORCC recycles Cl- across the basolateral membrane, allowing preferential HCO3- secretion.
authors.affiliation: Department of Physiology, University of Alberta, 7-46 Medical Sciences Bldg., Edmonton, Alberta, T6G 2H7 Canada.
authors.forename: Artur J
authors.initials: AJ
authors.lastname: Szkotak
authors.forename: S F Paul
authors.initials: SF
authors.lastname: Man
authors.forename: Marek
authors.initials: M
authors.lastname: Duszyk
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000378:metabolism; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000378:metabolism; D000838:Anions / Q000378:metabolism*; D016764:Cell Polarity; D002478:Cells, Cultured; D018118:Chloride Channels / Q000378:metabolism*; D006801:Humans; D007476:Ionophores / Q000378:metabolism; D009761:Nystatin / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010539:Permeability; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction; D014665:Vasodilator Agents / Q000378:metabolism
chemical_list: D000838:Anions; D018118:Chloride Channels; D007476:Ionophores; D018047:Receptors, Purinergic P1; D014665:Vasodilator Agents; D009761:Nystatin; D019830:Adenosine-5'-(N-ethylcarboxamide); D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid