Published ahead of print on May 30, 2003, doi:10.1165/rcmb.2003-0109OC
© 2003 American Thoracic Society DOI: 10.1165/rcmb.2003-0109OC The Role of the Basolateral Outwardly Rectifying Chloride Channel in Human Airway Epithelial Anion SecretionDepartments of Physiology and Medicine, University of Alberta, Edmonton, Alberta, Canada Address correspondence to: Dr. Marek Duszyk, Department of Physiology, University of Alberta, 7-46 Medical Sciences Bldg., Edmonton, Alberta, T6G 2H7 Canada. E-mail: marek.duszyk{at}ualberta.ca
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-
Abbreviations: A-kinase anchoring protein, AKAP • A1, A2A, A2B, A3, adenosine receptor subtypes • bronchial epithelial growth media, BEGM • intracellular Ca2+ concentration, [Ca2+]i • cystic fibrosis transmembrane conductance regulator, CFTR • glyceraldehyde-3-phosphate dehydrogenase, GAPDH • short-circuit current, Isc • 36Cl- apical to basolateral flux, JClAB • 36Cl- basolateral to apical flux, JClBA • 36Cl- net flux, JClnet • calculated net HCO3- flux, JHCO3net • Ca2+-dependent K+ channels, KCa • Krebs-Henseleit solution, KHS • normal human bronchial epithelia, NHBE • Na+-K+-2Cl-, NKCC • outwardly rectifying chloride channel, ORCC • closed probability, PC • protein kinase A, PKA • open probability, PO • transepithelial resistance, RT • reverse transcription polymerase chain reaction, RT-PCR • negative pipette potential, -VPIP This article has been cited by other articles:
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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. 
