Cl channels in basolateral TAL membranes. XVII. Kinetic properties of mcClC-Ka, a basolateral CTAL Cl- channel.
This paper describes the kinetics of Cl- flux through mcClC-Ka Cl- channels from basolateral membranes of mouse CTAL cells. We have cloned two separate but highly homologous Cl- channels, mmClC-Ka from cultured mouse MTAL cells and mcClC-Ka from cultured mouse CTAL cells. The mmClC-Ka and mcClC-Ka channels appear to mediate net Cl- absorption in the MTAL and CTAL, respectively. The kinetics of Cl- permeation through mmClC-Ka channels exhibit traditional criteria for a first-order process, including saturation kinetics. Thus mmClC-Ka channels operate functionally as if the channels were occupied by a single Cl- ion at any given time. In the present studies, we examined conductance-concentration relations in mcClC-Ka channels, and compared both mole-fraction effects and ion selectivity characteristics in mmClC-Ka and mcClC-Ka channels. In mcClC-Ka channels, we observed both self-block at high external Cl- concentrations and, at constant ionic strength, an anomalous mole-fraction effect using external solutions containing varying F-/Cl- concentrations. Neither effect was obtained in mmClC-Ka channels. These data are consistent with the possibility that Cl- permeation through mcClC-Ka channels involved multi-ion occupancy channels that expressed single-file behavior.
Winters
C J
CJ
Department of Internal Medicine, University of Arkansas College of Medicine and The John L. McClellan Veterans Hospital, Little Rock, USA.
Andreoli
T E
TE
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D002999:Clone Cells; D015640:Ion Channel Gating; D008051:Lipid Bilayers / Q000378:metabolism; D008138:Loop of Henle / Q000378:metabolism*; D008564:Membrane Potentials; D051379:Mice; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*
D018118:Chloride Channels; D002712:Chlorides; D008051:Lipid Bilayers; D015221:Potassium Channels