Cl- transport in basolateral renal medullary vesicles: II. Cl- channels in planar lipid bilayers.
The present studies examined some of the properties of Cl- channels in renal outer medullary membrane vesicles incorporated into planar lipid bilayers. The predominant channel was anion selective having a PCl/PK ratio of 10 and a unit conductance of 93 pS in symmetric 320 mM KCl. In asymmetric KCl solutions, the I-V relations conformed to the Goldman-Hodgkin-Katz equation. Channel activity was voltage-dependent with a gating charge of unity. This voltage dependence of channel activity may account, at least in part, for the striking voltage dependence of the basolateral membrane Cl- conductance of isolated medullary thick ascending limb segments. The Cl- channels incorporated into the planar bilayers were asymmetrical: the trans surface was sensitive to changes in ionized Ca2+ concentrations and insensitive to reducing KCl concentrations to 10 mM, while the cis side was insensitive to changes in ionized Ca2+ concentrations, but was inactivated by reducing KCl concentrations to 50 mM.
Reeves
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WB
Department of Internal Medicine, University of Arkansas College of Medicine, Little Rock 72205.
Andreoli
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TE
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D004553:Electric Conductivity; D004594:Electrophysiology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007679:Kidney Medulla / Q000378:metabolism* / Q000648:ultrastructure; D008051:Lipid Bilayers / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D062367:ortho-Aminobenzoates / Q000494:pharmacology
D002712:Chlorides; D007473:Ion Channels; D008051:Lipid Bilayers; D062367:ortho-Aminobenzoates; D011189:Potassium Chloride; C001209:fenamic acid; D002118:Calcium