Cholinergic regulation of voltage-dependent ca2+ channels in
porcine tracheal smooth muscle cells.
Yamakage, Michiaki, Carol A. Hirshman, and Thomas L. Croxton.
Departments of Anesthesiology & Critical Care Medicine and
Environmental Health Sciences, The Johns Hopkins Medical
Institutions, Baltimore, Maryland 21205
APStracts 2:0116L, 1995.
To investigate cholinergic regulation of voltage-dependent Ca2+
channels (VDCs) in airway smooth muscle, we measured inward currents
through VDCs in enzymatically-dispersed porcine tracheal smooth
muscle cells using conventional (10 mM Ca2+ as charge carrier) and
nystatin-perforated (5 mM Ba2+ as charge carrier) whole-cell patch
clamp techniques. Carbachol (CCh) had significant and dose-dependent
inhibitory effects on inward currents (12% with 10-7 M and 42% with
10-6 M) in perforated whole-cell clamp experiments, but had no effect
on currents in conventional whole- cell experiments. CCh also shifted
the steady-state inactivation curve to more negative potentials.
Further experiments tested the hypothesis that CCh inhibits VDCs in
part by the activation of protein kinase C (PKC). Phorbol 12,13
-diacetate, an exogenous PKC activator, inhibited currents through
VDCs and calphostin C, a specific PKC inhibitor, antagonized the
inhibitory effect of CCh. Furthermore, intracellular exposure to the
activating PKC fragment 530-558 using a pipette perfusion technique
also inhibited currents through VDCs. We conclude that cholinergic
receptor stimulation can inhibit inward Ca2+ currents through VDCs of
porcine tracheal smooth muscle and that this effect may be mediated
in part by activation of PKC.
Received 29 November 1994; accepted in final form 28 June 1995.
APS Manuscript Number L336-4.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.