Cl- channels in basolateral TAL membranes. XIV. Kinetic properties of a basolateral MTAL Cl- channel

Christopher J. Winters, W. Brian Reeves, Thomas E. Andreoli

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Background. This article reports studies on the kinetics of chloride (Cl-) conductance in Cl- channels fused into bilayers from basolaterally enriched vesicles from rabbit outer medulla. A considerable body of evidence indicates that these channels represent rbClC-Ka, a 77 kDa kidney-specific protein of the ClC family of Cl- channels. rbClC-Ka, a candidate channel for mediating net Cl- absorption in the medullary thick ascending limb (MTAL), has been cloned from rabbit outer medulla and localized by immunofluorescence to basolateral membranes of the MTAL. Thus, this is the first account, to our knowledge, of the kinetics of ion permeation through a renal Cl- channel mediating net basolateral Cl- absorption in the thick ascending limb of Henle (TALH), and this channel may represent rbClC-Ka. Methods. The electrophysiological properties of these channels were studied by fusing basolaterally enriched MTAL vesicles into planar bilayer membranes. Results. Cl- conductance through these channels was concentration dependent and saturable. The relationship between g(Cl) (pS) and symmetrical aqueous Cl- concentrations could be expressed in terms of the Michaelis equation with a limiting conductance (G(Cl)/(max), pS) of 114 pS at infinitely high aqueous Cl- concentrations and a K(1/2) of 163 mM Cl-. A log-log plot of the conductance-Cl- concentration relations, in the nonsaturating Cl- concentration range, had a slope of 0.91, that is, virtually unity. The relatively impermeant anion I- produced a voltage-dependent conductance blockade that could be overcome at high electric field strengths. Conclusions. The experimental data described earlier here fulfill the traditional criteria for a first-order process with a single Cl- ion occupying these channels at a given time. Although the channels may contain multiple ion binding sites, the latter function, in integral kinetic terms, as a single rate-limiting locus.

Original languageEnglish (US)
Pages (from-to)1444-1449
Number of pages6
JournalKidney International
Volume55
Issue number4
DOIs
StatePublished - Jan 1 1999
Externally publishedYes

Keywords

  • Bilayer
  • Chloride channels
  • Ion channels
  • Kinetics
  • Thick ascending limb

ASJC Scopus subject areas

  • Nephrology

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