Regulation of ca2+-activated k+ channels in pulmonary vascular
smooth muscle cells: role of nitric oxide.
Peng, Wei, John R. Hoidal, and Imad S. Farrukh.
Division of Respiratory, Critical Care and Occupational Pulmonary
Medicine, Department of Internal Medicine, The Veterans Affairs
Medical Center and University of Utah Health Science Center, Salt
Lake City, Utah 84132
APStracts 3:0208A, 1996.
Nitric oxide (NO ) is believed to mediate nitrovasodilators and
acetylcholine (ACh)-induced vasodilatation via increasing
intracellular guanosine 3O,5O-cyclic monophosphate (cGMP) levels. The
cellular mechanisms involved in NO -mediated pulmonary vasodilatation
are complex and include membrane hyperpolarization. Using the patch
-clamp technique in cell-attached and inside-out configurations, we
examined the effect of NO gas, 3-morpholinosydnomimine-hydrochloride
(SIN-1) and perfusate from ACh-stimulated human pulmonary arterial
endothelial cells (HPAEC), or endothelium-derived relaxing factors
(EDRF), on the Ca2+-dependent K+ channels (KCa) in isolated cultured
human pulmonary arterial smooth muscle cells (HPSMC). NO , SIN-1 and
EDRF caused similar increases in KCa activity. Inhibition of cGMP
generation with methylene blue or inhibiting the effect(s) of cGMP
with the cGMP antagonist, 8-bromo guanosine 3O,5O-cyclic
monophosphorothioate, Rp-isomer {(Rp)-cGMPS}, prevented the NO - and
SIN-1-mediated activation of KCa, respectively. Treating the HPAEC
with methylene blue blocked the EDRF-mediated activation of KCa in
HPSMC. The cGMP analog, 8-bromo-cGMP, increased KCa activity in
intact cells and in excised inside-out HPSMC membrane patches . In
presence of cGMP and ATP, the [alpha] isozyme of the cGMP-dependent
protein kinase (I[alpha] cGMP-PK) significantly increased KCa
activity, and the channel activation was further increased on adding
the protein phosphatase inhibitors okadaic acid or calyculin A.
Furthermore, the cGMP-mediated KCa activation was reduced by the
cyclic nucleotide-dependent protein kinase inhibitor H-8. Thus in
HPSMC, the mechanism of NO - and native EDRF-induced KCa activation
appears to be mediated via cGMP / I[alpha] cGMP-PK phosphorylation of
KCa.
Received 18 December 1995; accepted in final form 1 April 1996.
APS Manuscript Number A1319-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 May 96