title: Multiple modes of regulation of airway epithelial chloride secretion by extracellular ATP.
abstract: Cultured normal and cystic fibrosis (CF) airway epithelia were exposed to 5'-(N-ethylcarboxamido)-adenosine (NECA), ATP, or ionomycin. NECA activated a sustained, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-insensitive Cl- secretory response in normal but not CF, consistent with stimulation of the CF transmembrane conductance regulator (CFTR). In normal and CF, ionomycin or ATP induced Cl- secretion with an initial peak that was inhibited > 50% by DIDS, but in normals there was a prolonged current that was not inhibited by DIDS. The ATP and ionomycin responses in CF were of greater magnitude, and the prolonged phase was inhibited by DIDS. Although we expected ATP to regulate Cl- conductance through intracellular Ca2+ activity, ATP further stimulated Cl- secretion in tissues pretreated to maximally elevate intracellular Ca2+ activity. ATP also activated whole cell Cl- currents in cells dialyzed with 10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Thus ATP and ionomycin regulate a Cl- conductance that is distinct from CFTR, but the regulation by ATP is not tightly coupled to intracellular Ca2+ activity. Alternatively, ATP regulates separate Ca(2+)-sensitive and Ca(2+)-insensitive Cl- conductances. Furthermore, extracellular ATP activates DIDS-resistant Cl- secretion in normal but not CF cultured epithelia, consistent with activation of CFTR by extracellular ATP.
authors.affiliation: Department of Medicine, University of North Carolina at Chapel Hill 27599-7020.
authors.forename: M J
authors.initials: MJ
authors.lastname: Stutts
authors.forename: J G
authors.initials: JG
authors.lastname: Fitz
authors.forename: A M
authors.initials: AM
authors.lastname: Paradiso
authors.forename: R C
authors.initials: RC
authors.lastname: Boucher
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology*; D019830:Adenosine-5'-(N-ethylcarboxamide); D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000378:metabolism / Q000473:pathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004533:Egtazic Acid / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism*; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D012016:Reference Values; D012137:Respiratory System / Q000378:metabolism* / Q000473:pathology
chemical_list: C505032:CFTR protein, human; D002712:Chlorides; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D019830:Adenosine-5'-(N-ethylcarboxamide); D004533:Egtazic Acid; D015759:Ionomycin; D000255:Adenosine Triphosphate; D000241:Adenosine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium