Atp-sensitive potassium channels in cultured arterial segments.
Kleppisch, Thomas, Barbara Winter, and Mark T. Nelson.
Department of Pharmacology, University of Vermont, 55A South Park
Drive, Colchester, VT 05446-2500
APStracts 3:0240H, 1996.
Organ cultures of arteries have been used to study growth responses,
proliferation and contractility. However, the function of specific
ion channels in cultured arteries has not been investigated. ATP
-sensitive potassium (KATP) channels play an important role in the
control of arterial tone. The goal of this study was to determine the
functional state of KATP channels in arteries kept in culture.
Segments from rabbit mesenteric arteries were cultured in a DMEM/F12
based medium for 2-7 days. To explore the properties of KATP channels
in cultured arteries, effects of KATP channel modulators and other
vasoactive substances on isometric force, the density and modulation
of KATP currents in single smooth muscle cells isolated from cultured
vessels were examined. Isometric contractions were measured using a
resistance vessel myograph. Whole-cell KATP currents were recorded
using the patch clamp technique. Membrane capacitance and KATP
current density in single smooth muscle cells from freshly-dissected
(control) and cultured arteries were not altered. At -60 mV,
glibenclamide-sensitive currents in the presence of the potassium
channel opener, pinacidil, were -4.7 +/- 1.2 pA/pF (control), -4.7
+/- 0.6 pA/pF (2 days), -4.6 +/- 0.7 pA/pF (4 days), respectively.
Inhibitory modulation of KATP currents in arterial smooth muscle also
remained intact for 4 days in culture; the vasoconstrictor, histamine
(10 [mu]M), reduced glibenclamide-sensitive currents in the presence
of pinacidil by 61.2 +/- 2.8 % (control), 42.4 +/- 10.1 % (2 days)
and 41.2 +/- 6.1 % (4 days). Control as well as cultured arteries (1
-7 days), relaxed to pinacidil in a dose-dependent manner. Half
-maximal effective concentrations of pinacidil were 0.42 [mu]M
(control), 0.24 [mu]M (2 days), 0.23 [mu]M (5 days) and 0.51 [mu]M (7
days), whereas maximal relaxations to pinacidil were 62.9 %
(control), 47.5 % (2 days), 37.5 % (5 days) and 55.7 % (7 days).
Cultured arteries constricted to histamine, norepinephrine and
serotonin, though responses to histamine and norepinephrine
diminished by 30-50% after 5 days in culture. The relaxant effect of
acetylcholine was not maintained in cultured arteries. Sodium
nitroprusside, however, effectively relaxed arteries cultured for 2
to 7 days. The data indicate that using the culture model described,
KATP channels in arterial smooth muscle remained functional and
contractile responses in arterial segments were maintained for up to
7 days. These results suggest that this approach can be used to study
either long-term regulation of KATP channels or the role of this
channel type in the growth responses.
Received 15 March 1996; accepted in final form 27 March 1996.
APS Manuscript Number H248-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96