title: Anion secretion by the inner medullary collecting duct. Evidence for involvement of the cystic fibrosis transmembrane conductance regulator.
abstract: It is well established that the terminal renal collecting duct is capable of electrogenic Na+ absorption. The present experiments examined other active ion transport processes in primary cultures of the rat inner medullary collecting duct. When the amiloride analogue benzamil inhibited electrogenic Na+ absorption, cAMP agonists stimulated a transmonolayer short circuit current that was not dependent on the presence of Na+ in the apical solution, but was dependent on the presence of Cl- and HCO3-. This current was not inhibited by the loop diuretic bumetanide, but was inhibited by ouabain, an inhibitor of the Na+/K+ pump. The current was reduced by anion transport inhibitors, with a profile similar to that seen for inhibitors of the cystic fibrosis transmembrane conductance regulator (CFATR) Cl- channel. Using several PCR strategies, we demonstrated fragments of the predicted lengths and sequence identity with the rat CFTR. Using whole-cell patch-clamp analysis, we demonstrated a cAMP-stimulated Cl- current with characteristics of the CFTR. We conclude that the rat inner medullary collecting duct has the capacity to secrete anions. It is highly likely that the CFTR Cl- channel is involved in this process.
authors.affiliation: Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
authors.forename: R F
authors.initials: RF
authors.lastname: Husted
authors.forename: K A
authors.initials: KA
authors.lastname: Volk
authors.forename: R D
authors.initials: RD
authors.lastname: Sigmund
authors.forename: J B
authors.initials: JB
authors.lastname: Stokes
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000838:Anions / Q000378:metabolism; D001483:Base Sequence; D001639:Bicarbonates / Q000378:metabolism; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism* / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D017931:DNA Primers; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D006016:Glycolates / Q000494:pharmacology; D007679:Kidney Medulla / Q000187:drug effects / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D008969:Molecular Sequence Data; D009579:Nitrobenzoates / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar
chemical_list: D000838:Anions; D001639:Bicarbonates; D018118:Chloride Channels; D002712:Chlorides; D017931:DNA Primers; D006016:Glycolates; D008565:Membrane Proteins; D009579:Nitrobenzoates; C013407:benzamil; D002034:Bumetanide; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; C015765:MK 473; D010042:Ouabain; D000584:Amiloride; D000242:Cyclic AMP; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D005905:Glyburide; D015056:1-Methyl-3-isobutylxanthine