AJP - Cell Physiology, Vol 272, Issue 4 C1151-C1159, Copyright © 1997 by American Physiological Society

ARTICLES

Modulation of maxi-K+ channels by voltage-dependent Ca2+ channels and methacholine in single airway myocytes

Y. X. Wang, B. K. Fleischmann and M. I. Kotlikoff
Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104-6046, USA.

The role of Ca2+ influx through voltage-dependent Ca2+ channels and the inhibitory effects of methacholine on large-conductance Ca2+-activated K+ (K(Ca)) channels (maxi-K+ channels) were studied in voltage-clamped (nystatin), fura 2-loaded airway smooth muscle cells. Spontaneous transient outward currents (STOCs) were strongly coupled to voltage-dependent Ca2+ channel activity; activity was suppressed by nisoldipine and Cd2+ and increased by BAY K 8644 within seconds. Moreover, release of intracellular Ca2+ by caffeine or cyclopiazonic acid only partially suppressed STOCs, and the remainder were almost completely blocked by nisoldipine. Methacholine suppressed STOCs but also significantly decreased the mean outward current. Whole cell current inhibition was observed in the presence of 4-aminopyridine but not in the presence of charybdotoxin. Caffeine inhibited STOCs but macroscopic outward currents were not altered. In the continued presence of caffeine, methacholine abolished the remaining STOCs and decreased the mean K+ current. We conclude that STOCs are activated by influx of Ca2+ through plasmalemmal voltage-dependent Ca2+ channels, as well as by release of Ca2+ from intracellular stores, and muscarinic stimulation depresses the mean K(Ca) current via a pathway independent of the depletion of intracellular Ca2+ stores.

This article has been cited by other articles:

				Y. Yang, T. V. Murphy, S. R. Ella, T. H. Grayson, R. Haddock, Y. T. Hwang, A. P. Braun, G. Peichun, R. J. Korthuis, M. J. Davis, et al. Heterogeneity in function of small artery smooth muscle BKCa: involvement of the \#946;1-subunit J. Physiol., June 15, 2009; 587(12): 3025 - 3044. [Abstract] [Full Text] [PDF]

				G. Martin, R. J. O'Connell, A. Z. Pietrzykowski, S. N. Treistman, M. F. Ethier, and J. M. Madison Interleukin-4 activates large-conductance, calcium-activated potassium (BKCa) channels in human airway smooth muscle cells Exp Physiol, July 1, 2008; 93(7): 908 - 918. [Abstract] [Full Text] [PDF]

				B. Liu, A. M. Freyer, and I. P. Hall Bradykinin activates calcium-dependent potassium channels in cultured human airway smooth muscle cells Am J Physiol Lung Cell Mol Physiol, April 1, 2007; 292(4): L898 - L907. [Abstract] [Full Text] [PDF]

				L. J. Janssen Ionic mechanisms and Ca2+ regulation in airway smooth muscle contraction: do the data contradict dogma? Am J Physiol Lung Cell Mol Physiol, June 1, 2002; 282(6): L1161 - L1178. [Abstract] [Full Text] [PDF]

				J. H. Jaggar Intravascular pressure regulates local and global Ca2+ signaling in cerebral artery smooth muscle cells Am J Physiol Cell Physiol, August 1, 2001; 281(2): C439 - C448. [Abstract] [Full Text] [PDF]

				L. Tao, Y. Huang, and J.-P. Bourreau Control of the mode of excitation-contraction coupling by Ca2+ stores in bovine trachealis muscle Am J Physiol Lung Cell Mol Physiol, October 1, 2000; 279(4): L722 - L732. [Abstract] [Full Text] [PDF]

				L. J. Janssen, P. A. Betti, S. J. Netherton, and D. K. Walters Superficial buffer barrier and preferentially directed release of Ca2+ in canine airway smooth muscle Am J Physiol Lung Cell Mol Physiol, May 1, 1999; 276(5): L744 - L753. [Abstract] [Full Text] [PDF]

				D. Salvail, M. Dumoulin, and E. Rousseau Direct modulation of tracheal Cl--channel activity by 5,6- and 11,12-EET Am J Physiol Lung Cell Mol Physiol, September 1, 1998; 275(3): L432 - L441. [Abstract] [Full Text] [PDF]

				J. H. Jaggar, A. S. Stevenson, and M. T. Nelson Voltage dependence of Ca2+ sparks in intact cerebral arteries Am J Physiol Cell Physiol, June 1, 1998; 274(6): C1755 - C1761. [Abstract] [Full Text] [PDF]

				Y.-X. Wang and M. I. Kotlikoff Inactivation of calcium-activated chloride channels in smooth muscle by calcium/calmodulin-dependent protein kinase PNAS, December 23, 1997; 94(26): 14918 - 14923. [Abstract] [Full Text] [PDF]

				A. D. Bonev, J. H. Jaggar, M. Rubart, and M. T. Nelson Activators of protein kinase C decrease Ca2+ spark frequency in smooth muscle cells from cerebral arteries Am J Physiol Cell Physiol, December 1, 1997; 273(6): C2090 - C2095. [Abstract] [Full Text] [PDF]