Pharmacology of atp-sensitive k+ currents in smooth muscle cells
from rabbit mesenteric artery.
Quayle, John M., Adrian D. Bonev, Joseph E. Brayden, and Mark T.
Nelson.
Department of Pharmacology, University of Vermont Medical Research
Facility, 55A South Park Drive, Colchester, Vermont 05446, Current
address: Department of Cell Physiology and Pharmacology, University
of Leicester, University Road, Leicester, LE1 9HN. England
APStracts 2:0190C, 1995.
The inference that KATP channels are involved in arterial responses to
synthetic K+ channel openers, hypoxia, adenosine, calcitonin gene
-related peptide has relied on the sensitivity of these responses to
the sulfonylureas, glibenclamide and tolbutamide, and to
tetraethylammonium (TEA+). The inhibition of ATP-sensitive K+ (KATP)
currents by glibenclamide, tolbutamide, and TEA+ was investigated in
single smooth muscle cells from rabbit mesenteric artery using the
whole cell patch clamp technique. The synthetic K+ channel openers,
pinacidil (half-activation, 0.6 [mu]M), cromakalim (half-activation,
1.9 [mu]M) and diazoxide (half-activation, 37.1 [mu]M) activated
potassium-selective currents which were blocked by glibenclamide.
Elevation of pipette (intracellular) ATP decreased K+ currents
induced by pinacidil. Half-inhibition of KATP currents by
glibenclamide and tolbutamide occurred at 101 nM and 351 [mu]M,
respectively. KATP currents were also inhibited by external TEA+,
with a half inhibition at a concentration of 6.2 mM. The results
indicate that glibenclamide is an effective inhibitor of KATP
channels in arterial smooth muscle, and tolbutamide and TEA+ are much
less effective. Further, these results support numerous functional
studies that have demonstrated that the vasorelaxations to K+ channel
openers are inhibited by <10 [mu]M glibenclamide but not by <1 mM
TEA+.
Received 6 January 1995; accepted in final form 24 April 1995.
APS Manuscript Number C13-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 16 May 1995.