Functional identification of a sarcolemmal chloride channel from
bovine tracheal smooth muscle.
Salvail, Dany, Abderrahmane Alioua, and Eric Rousseau.
Le Bilarium, Department of Physiology & Biophysics, Faculty of
Medicine, University of Sherbrooke, Sherbrooke, Qc, Canada, J1H
5N4
APStracts 3:0191C, 1996.
The biophysical and pharmacological characteristics of unitary Cl-
currents from bovine tracheal smooth muscle cells were studied
following reconstitution of microsomal vesicles into planar lipid
bilayers. Two types of currents were recorded simultaneously in KCl
buffer: the well-defined Ca2+-dependent K+ current (GKCa) and a much
smaller Cl - current, indicating that the Cl - channels under
scrutiny originate from the same membrane as the plasma membrane of
airway smooth muscle (ASM) cells. The GKCa activities were eliminated
by the use of CsCl buffer. The average unitary Cl- conductance
measured in 50 mM trans / 250 mM cis CsCl was 77 +/- 6 pS (n = 21)
and the reversal potential measured in various CsCl gradients
followed ECl as determined from the Nernst equation. In contrast with
the previous reports describing the Ca2+ -sensitivity of macroscopic
ASM Cl- currents, this channel was found to be insensitive to
cytoplasmic and extracellular Ca2+ levels. Phosphorylation cocktails
including PKA, PKG or PKC did not alter the activity of the channel,
nor did changes in pH. Amongst a series of Cl- channel inhibitors,
4,4'-diisothiocyanato 2,2'-disulfonic acid (DIDS) (EC50 = 30 [mu]M)
and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) (EC 50 = 130
[mu]M) were the most potent blockers of the current examined. The
exact role of this surface Cl- conductance remains unclear, and its
involvement in cellular activity needs further investigation.
Received 13 February 1996; accepted in final form 6 June 1996.
APS Manuscript Number C82-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96