Iloprost activates ca-activated k channels of single vascular
smooth muscle cells, role of camp-dependent protein kinase.
Schubert, Rudolf, Vladimir N. Serebryakov, Heidrun Engel, and Hans
-Heinrich Hopp.
University of Rostock, Institute of Physiology, PSF 100888, D-18055
Rostock, Germany, Institute of Experimental Cardiology, Cardiology
Research Center, Academy of Medical Sciences, 3rd Cherepkovskaya
Street 15A, 121552 Moscow, Russia
APStracts 3:0146C, 1996.
Using the patch-clamp technique the effect of iloprost on the activity
of calcium-activated (KCa) potassium channels of freshly isolated rat
tail artery smooth muscle cells was investigated. In the whole-cell
configuration the outward current, determined largely by KCa
channels, was enhanced 1.73+/-0.11-fold by 5x10-7 M iloprost, 1.80+/
-0.12-fold by 10-4 M Sp-5,6-DCl-cBIMPS, a specific activator of the
cAMP-dependent protein kinase (PKA), and 2.78+/-0.95-fold by 10 U/ml
of the catalytic subunit of PKA together with 10-4_ M MgATP, whereas
the heat-inactivated catalytic subunit of PKA together with MgATP was
without effect. 5x10-7 M iloprost increased this current 1.70+/-0.27
-fold after pretreatment of the cells with 10-6 M okadaic acid, a
specific phosphatase inhibitor, but did not alter this current after
pretreatment of the cells with 2x10-4 Rp-8-CPT-cAMPS, a specific PKA
inhibitor. In the cell-attached configuration the activity of KCa
channels was enhanced 2.48+/-0.44-fold by 5x10-7 M iloprost and
2.09+/-0.07-fold by 10-4 M Sp-5,6-DCl-cBIMPS. 5x10-7 M iloprost did
not alter the intracellular calcium concentration in these cells
measured using INDO-1. In the inside-out configuration the activity
of KCa channels was increased 87.12+/-45.04-fold by 10 U/ml of the
catalytic subunit of PKA together with 10-4_ M MgATP, whereas no
effect was observed after application of the catalytic subunit of PKA
together with its regulatory subunit and MgATP. MgATP, cAMP or the
catalytic subunit of PKA alone also did not change KCa channel
activity. Thus, these results show, that iloprost is able to activate
KCa channels of freshly isolated rat tail artery smooth muscle cells
and suggest that this effect is mediated by a PKA-induced
phosphorylation of the channel.
Received 24 July 1995; accepted in final form 28 March 1996.
APS Manuscript Number C452-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96