Nitric oxide mediates outward potassium currents in opossum
esophageal circular smooth muscle.
Jury, Jennifer, K. R. Boev, and E. E. Daniel.
Dept. of Biomedical Sciences, McMaster University, Health Sciences
Centre, 1200 Main St. Hamilton Ont. Canada L8N 3Z5, Institute of
Physiology,Bulgarian Academy of Sciences, Sofia, Bulgaria
APStracts 2:0253G, 1995.
Single smooth muscle cells from the opossum BCM were isolated and
whole cell currents were characterized the whole cell patch clamp
technique. When the cells were held at -50mV and depolarized to 70mV
in 20mV increments, initial small inactivating inward currents were
evoked (-30 to 30mV) followed by larger sustained outward
currents.Depolarization from a holding potential of -90mV evoked an
initial, fast inactivating outward current sensitive to 4
-aminopyridine but not to high levels of EGTA. The outward currents
reversed near EK and were abolished when KCl was replaced by CsCl in
the pipette solution. The sustained outward current which was
inhibited by quinine and cesium. High EGTA in the pipette solution
reduced but did not abolish the sustained outward currents,
suggesting that both Ca2+-dependent and independent currents were
evoked. The nitric oxide releasing agents, Sin-1 and NaP, 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 (CPA), 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
calcium release from the SR stores.
Received 22 September 1994; accepted in final form 18 November
1995.
APS Manuscript Number G372-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 12 December 95