Cl- channels in basolateral renal medullary vesicles ix. comparison
of channels from excised patches of cultured mouse mtal cells and
basolateral medullary vesicles.
Reeves, W. Brian, Christopher J. Winters, Dragana M. Filipovic, Thomas
E. Andreoli.
Division of Nephrology, Department of Internal Medicine, University
of Arkansas College of Medicine and John L. McClellan Veterans
Administration Hospital, Little Rock, Arkansas
APStracts 2:0089F, 1995.
The experiments in this paper compared Cl- channels fused into
bilayers from rabbit outer medullary vesicles with Cl- channels in
excised patches of basolateral membranes from cultured mouse mTAL
cells; and evaluated whether the latter were plausible candidates for
the Cl- channels mediating net NaCl absorption in microperfused mouse
mTAL segments. The unique signature characteristics of Cl- channels
incorporated into lipid bilayers from outer medullary vesicles
include: activation of Po by increases in the Cl- concentrations
bathing intracellular faces; activation of Po by (PKA + ATP) when the
Cl- concentrations bathing intracellular faces are low; and no effect
of (PKA + ATP) on Po with high cytoplasmic face Cl- concentrations.
These same properties were observed in Cl- channels studied using
excised patches of basolateral membranes from mouse mTAL cells.
Moreover, both in bilayers and in excised patches, the sharpest
fractional increase in Cl- channel Po occurred with cytosolic face
Cl- concentration increases to values similar to the ADH-dependent
values of intracellular Cl- activity in microperfused mouse mTAL
segments. And these fractional Po increases were adequate to account
quantitatively for the ADH-dependent increase in basolateral membrane
Cl- conductance in microperfused mouse mTAL segments. Thus the
excised patch basolateral Cl- channels reported in this paper are
reasonable candidates for those mediating net Cl- absorption in the
mTAL.
Received 22 September 1994; accepted in final form 3 April 1995.
APS Manuscript Number F340-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.