Chloride channels in the apical membrane of cortical collecting duct cells.
Ion channels in the apical membrane of cortical collecting duct (CCD) cells in culture were studied by the patch-clamp technique. CCD cells from rabbit kidney were isolated by solid-phase immunoadsorption with a monoclonal antibody. The majority of CCD cells (93%) had phenotypic characteristics similar to intercalated cells (ICC). Although Cl- channels were present in the apical membrane of the ICC cells, they were rarely active in cell-attached patches; however, channels were activated after patch excision. In inside-out patches, the channels exhibited rapid flickering, substrates, and large unitary currents. The single-channel conductance was 303 pS, the Cl(-)-to-Na+ permeability ratio was 10:1 and the Cl(-)-to-HCO3- permeability ratio was 1.5:1. The channel was inhibited by the Cl- channel blockers 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, diphenylamine carboxylic acid, and 5-nitro-2-(3-phenylpropylamino)-benzoic acid. Although a reduction in the cytoplasmic Ca2+ concentration inhibited channel activity in both inside-out patches and cell-attached patches, alterations of Ca2+ within the physiological range did not change the channel open probability. Finally, changing the cytoplasmic pH (6.5 to 8.0) did not alter the open probability. Thus a large conductance anion channel is present in the apical membrane of CCD cells in culture. This channel may be involved in cell volume regulation or in Cl- and HCO3- secretion.
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Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03756.
Schwiebert
E M
EM
Fejes-Toth
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Naray-Fejes-Toth
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A
Karlson
K H
KH
McCann
F V
FV
Stanton
B A
BA
D000818:Animals; D000911:Antibodies, Monoclonal; D001639:Bicarbonates / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D001639:Bicarbonates; D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D002118:Calcium