AJP - Gastrointestinal and Liver Physiology, Vol 270, Issue 6 932-G938, Copyright © 1996 by American Physiological Society

ARTICLES

Nitric oxide mediates outward potassium currents in opossum esophageal circular smooth muscle

J. Jury, K. R. Boev and E. E. Daniel
Department of Biomedical Science, McMaster University, Hamilton, Ontario, Canada.

Single smooth muscle cells from the opossum body circular muscle were isolated and whole cell currents were characterized by the whole cell patch-clamp technique. When the cells were held at -50 mV and depolarized to 70 mV in 20-mV increments, initial small inactivating inward currents were evoked (-30 to 30 mV) followed by larger sustained outward currents. Depolarization from a holding potential of -90 mV evoked an initial fast inactivating outward current sensitive to 4-aminopyridine but not to high levels of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). The outward currents reversed near K+ equilibrium potential and were abolished when KCl was replaced by CsCl in the pipette solution. The sustained outward current was inhibited by quinine and cesium. High EGTA in the pipette solution reduced but did not abolish the sustained outward currents, suggesting that both Ca(2+)-dependent and -independent currents were evoked. The nitric oxide (NO)-releasing agents Sin-1 and sodium nitroprusside increased outward K+ currents. High levels of EGTA in the pipette solution abolished the increase in outward current induced by Sin-1. The presence of cyclopiazonic acid, an inhibitor of the sarcoplasmic reticulum (SR) Ca2+ pump, blocked the effects of NO-releasing agents. We conclude that NO release activates K+ outward currents in opossum esophagus circular muscle, which may depend on Ca2+ release from the SR stores.

This article has been cited by other articles:

				S. J. Hwang, N. O'Kane, C. Singer, S. M. Ward, K. M. Sanders, and S. D. Koh Block of inhibitory junction potentials and TREK-1 channels in murine colon by Ca2+ store-active drugs J. Physiol., February 15, 2008; 586(4): 1169 - 1184. [Abstract] [Full Text] [PDF]

				A. F. El-Yazbi, W. J. Cho, G. Boddy, R. Schulz, and E. E. Daniel Impact of caveolin-1 knockout on NANC relaxation in circular muscles of the mouse small intestine compared with longitudinal muscles Am J Physiol Gastrointest Liver Physiol, February 1, 2006; 290(2): G394 - G403. [Abstract] [Full Text] [PDF]

				Y. Zhang and W. G. Paterson Role of Ca2+-activated Cl- channels and MLCK in slow IJP in opossum esophageal smooth muscle Am J Physiol Gastrointest Liver Physiol, July 1, 2002; 283(1): G104 - G114. [Abstract] [Full Text] [PDF]

				R. K. Goyal and X. D. He Evidence for NO · redox form of nitric oxide as nitrergic inhibitory neurotransmitter in gut Am J Physiol Gastrointest Liver Physiol, November 1, 1998; 275(5): G1185 - G1192. [Abstract] [Full Text] [PDF]

				H. KURIYAMA, K. KITAMURA, T. ITOH, and R. INOUE Physiological Features of Visceral Smooth Muscle Cells, With Special Reference to Receptors and Ion Channels Physiol Rev, July 1, 1998; 78(3): 811 - 920. [Abstract] [Full Text] [PDF]

				Y. Zhang, F. Vogalis, and R. K. Goyal Nitric oxide suppresses a Ca2+-stimulated Cl- current in smooth muscle cells of opossum esophagus Am J Physiol Gastrointest Liver Physiol, May 1, 1998; 274(5): G886 - G890. [Abstract] [Full Text] [PDF]

				A. M. F. Salapatek, Y.-F. Wang, Y.-K. Mao, M. Mori, and E. E. Daniel Myogenic NOS in canine lower esophageal sphincter: enzyme activation, substrate recycling, and product actions Am J Physiol Cell Physiol, April 1, 1998; 274(4): C1145 - C1157. [Abstract] [Full Text] [PDF]