title: Extracellular alkalinization stimulates calcium-activated chloride conductance in cystic fibrosis human airway epithelial cells.
abstract: BACKGROUND
  The pH of the airway surface liquid (ASL) plays a pivotal role in maintaining the proper function of the respiratory epithelium. In patients with cystic fibrosis (CF) acidic ASL has been observed. Thus, alkalinization of ASL itself might be beneficial in CF. The aim of this study was to investigate the role of extracellular pH (pH(o)) on the alternative Ca(2+)-activated Cl(-) channels (CaCCs) in CF airway epithelial cells.
  
  
  METHODS
  The [Ca(2+)](i) and viability of CF airway epithelial cells (IB3-1) were assessed using Fluo-3/AM and YO-PRO-1 fluorescent dyes, respectively. Ion currents were detected in whole-cell configuration using the patch clamp technique.
  
  
  RESULTS
  Extracellular alkalinization (pH(o) 8.2) stimulated Ca(2+) entry and inward currents in low Na(+) containing medium. The inward currents were blocked by the removal of extracellular Ca(2+), chelating cytosolic Ca(2+), as well as by the application of niflumic acid and DIDS. While Zn(2+) promoted sustained Ca(2+) entry in pH(o)-dependent manner, it inhibited the anion conductance. The low external Na(+) concentrations and alkaline pH(o) were well tolerated by the cells.
  
  
  CONCLUSIONS
  Stimulation of CaCCs could be achieved by alkalinization of the extracellular environment in CF airway epithelial cells. Zn(2+) directly blocked, however indirectly enhanced the activity of Cl(-) conductance.
authors.affiliation: Institute of Human Physiology and Clinical Experimental Research, Semmelweis University, Budapest, Hungary. tamas.danko@eok.sote.hu
authors.forename: Tamás
authors.initials: T
authors.lastname: Dankó
authors.forename: Dóra
authors.initials: D
authors.lastname: Hargitai
authors.forename: Agnes
authors.initials: A
authors.lastname: Pataki
authors.forename: Hasif
authors.initials: H
authors.lastname: Hakim
authors.forename: Miklós
authors.initials: M
authors.lastname: Molnár
authors.forename: Akos
authors.initials: A
authors.lastname: Zsembery
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000814:Aniline Compounds / Q000737:chemistry / Q000494:pharmacology; D001583:Benzoxazoles / Q000737:chemistry / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000503:physiopathology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D005456:Fluorescent Dyes / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009544:Niflumic Acid / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011806:Quinolinium Compounds / Q000737:chemistry / Q000494:pharmacology; D020545:Respiratory Mucosa / Q000503:physiopathology*; D014966:Xanthenes / Q000737:chemistry / Q000494:pharmacology; D017967:Zinc Compounds / Q000494:pharmacology
chemical_list: D000814:Aniline Compounds; D001583:Benzoxazoles; D018118:Chloride Channels; D002712:Chlorides; D005456:Fluorescent Dyes; D011806:Quinolinium Compounds; D014966:Xanthenes; D017967:Zinc Compounds; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C089813:YO-PRO 1; C059715:Fluo-3; D009544:Niflumic Acid; C016837:zinc chloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium