TY - JOUR
T1 - Cl- channels in basolateral TAL membranes. XIV. Kinetic properties of a basolateral MTAL Cl- channel
AU - Winters, Christopher J.
AU - Reeves, W. Brian
AU - Andreoli, Thomas E.
N1 - Funding Information:
This work was supported by NIH Grant (5 R01 DK25540) and a Veterans Administration Merit Review Grant to Prof. Andreoli. We are grateful to Dr. Ludwika Zimniak for valuable dialogue. The technical assistance provided by Ms. Anna Grace Stewart and the secretarial assistance provided by Ms. Clementine Whitman are greatly appreciated. Dr. Reeves is an Established Investigator of the American Heart Association (95-1450).
PY - 1999
Y1 - 1999
N2 - 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.
AB - 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.
KW - Bilayer
KW - Chloride channels
KW - Ion channels
KW - Kinetics
KW - Thick ascending limb
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U2 - 10.1046/j.1523-1755.1999.00401.x
DO - 10.1046/j.1523-1755.1999.00401.x
M3 - Article
C2 - 10201009
AN - SCOPUS:0032924239
VL - 55
SP - 1444
EP - 1449
JO - Kidney International
JF - Kidney International
SN - 0085-2538
IS - 4
ER -