Anion secretion by the inner medullary collecting duct. Evidence for involvement of the cystic fibrosis transmembrane conductance regulator.
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.
Husted
R F
RF
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
Volk
K A
KA
Sigmund
R D
RD
Stokes
J B
JB
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
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