A fast transient outward current in cultured cells from human
pulmonary artery smooth muscle.
James, Andrew F., Toshikazu Okada, Minoru Horie.
International Research Laboratories, Ciba-Geigy Japan Ltd.,
TAKARAZUKA 665, Third Department of Internal Medicine, Kyoto
University, KYOTO 606 Japan.
APStracts 2:0080H, 1995.
A voltage-dependent transient outward (Ito) current was observed in
cells cultured from human pulmonary artery smooth muscle when K+, but
not Cs+, was the dominant cation in the pipette solution. In 30% of
cells investigated using the Cs+-pipette solution. a tetrodotoxin
-sensitive inward current (Iin) dependent on extracellular Na+ was
evoked from depolarizations positive to -30 mV. Iin showed voltage
-dependent inactivation with a V50% of -75.53 +/- 0.81 mV and Vs of
-10.73 +/- 0.01 mV. In the presence of 1 [mu]M tetrodotoxin, the
outward current was rapidly evoked by depolarizations positive to -40
mV and decayed with a single exponential time course (t = 9.9 +/- 1.1
ms, Vp = +50 mV). Ito also showed voltage-dependent inactivation with
a V50% of -70.9 +/- 2.63 mV and Vs of -7.7 +/- 0.03 mV. Ito was
inhibited concentration-dependently by the K+ channel blocker, 4
-aminopyridine, with an EC50 of 36.5 +/- 2.8 [mu]M. These cells
possess voltage-dependent currents characteristic of the K+-selective
fast transient outward and Na+-selective inward currents of smooth
muscle cells.
Received 17 May 1994; accepted in final form 6 January 1995.
APS Manuscript Number H419-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.