Effects of arachidonic acid on a-type potassium currents in smooth
muscle cells of the guinea-pig.
Nagano, Norihiro, Yuji Imaizumi, and Minoru Watanabe.
Department of Chemical Pharmacology, Faculty of Pharmacological
Science, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya
467, Japan
APStracts 3:0357C, 1996.
Effects of arachidonic acid (AA) and related fatty acids on Ca2+
independent transient (A-type) K+ current (IA) were examined in
single myocytes of guinea pig vas deferens, ureter and proximal
colon, as well as rabbit vas deferens. The peak amplitude of IA was
reduced by external application of AA (IC50=1 [mu]M). The blocking
effect was not changed significantly by indomethacin,
nordihydroguaiaretic acid, GDP[beta]S or GTP[tau]S. Pharmacological
studies suggested that the effect of AA was not mediated by
activation of protein kinase A or C, or tyrosine kinase. AA (20:4)
was the most potent of the four types of all-cis-eicosanoic acids
with 2-5 double bonds (20:2-20:5) which were tested. IA-like current
in cardiac atrial myocytes of the rabbit was not affected
significantly by 30 [mu]M AA. These results indicate that AA itself
directly blocks A-type K+ channels. A relationship between
stereospecific chemical structure of fatty acids and their blockade
of A-type K channels is suggested. A-type K channels in smooth muscle
cells can be clearly resolved from those in atrial myocytes by the
responses to AA.
Received 2 July 1996; accepted in final form 11 October 1996.
APS Manuscript Number C372-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996