title: pH-regulated chloride secretion in fetal lung epithelia.
abstract: The fetal lung actively transports chloride across the airway epithelium. ClC-2, a pH-activated chloride channel, is highly expressed in the fetal lung and is located on the apical surface of the developing respiratory epithelium. Our goal was to determine whether acidic pH could stimulate chloride secretion in fetal rat distal lung epithelial cells mounted in Ussing chambers. A series of acidic solutions stimulated equivalent short-circuit current (I(eq)) from a baseline of 28 +/- 4.8 (pH 7.4) to 70 +/- 5 (pH 6.2), 114 +/- 12.8 (pH 5.0), and 164 +/- 19.2 (pH 3.8) microA/cm(2). These changes in I(eq) were inhibited by 1 mM cadmium chloride and did not result in large changes in [(3)H]mannitol paracellular flux. Immunofluorescent detection by confocal microscopy revealed that ClC-2 is expressed along the luminal surface of polarized fetal distal lung epithelial cells. These data suggest that the acidic environment of the fetal lung fluid could activate chloride channels contributing to fetal lung fluid production and that the changes in I(eq) seen in these Ussing studies may be due to stimulation of ClC-2.
authors.affiliation: Eudowood Division of Respiratory Sciences, Department of Pediatrics, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA. cblaisdell@som.umaryland.edu
authors.forename: C J
authors.initials: CJ
authors.lastname: Blaisdell
authors.forename: R D
authors.initials: RD
authors.lastname: Edmonds
authors.forename: X T
authors.initials: XT
authors.lastname: Wang
authors.forename: S
authors.initials: S
authors.lastname: Guggino
authors.forename: P L
authors.initials: PL
authors.lastname: Zeitlin
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D000090007:CLC-2 Chloride Channels; D019256:Cadmium Chloride / Q000494:pharmacology; D018118:Chloride Channels / Q000378:metabolism / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D004553:Electric Conductivity; D004847:Epithelial Cells / Q000378:metabolism; D005333:Fetus / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008168:Lung / Q000196:embryology*; D008353:Mannitol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
chemical_list: D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D002712:Chlorides; D008353:Mannitol; D006859:Hydrogen; D019256:Cadmium Chloride