Dual regulation of phospholipase a2 and prostacyclin production by
g proteins in bovine aortic endothelial cells.
Rosenstock, Moti, Abraham Danon, and Gilad Rimon.
Dept. of Clinical Pharmacology, The Corob Center for Health
Sciences, Ben-Gurion University and Soroka Medical Center, P.O.B.
653, Beer-Sheva 84105, Israel
APStracts 3:0068C, 1996.
Sodium fluoride (NaF), a non selective activator of heterotrimeric
guanine nucleotide-binding proteins (G proteins), increased the
release of arachidonic acid (AA) and prostacyclin (PGI2) production
in bovine aortic endothelial cells (BAEC) at low concentrations (40
-60 mM). On the other hand, higher concentrations (100 mM) inhibited
phospholipase A2 (PLA2), as compared to the basal activity.
Intracellular calcium levels did not rise after treatment with
stimulatory concentrations of NaF, and moreover, neither neomycin nor
Ca2+-free medium affected the biphasic pattern of PGI2 synthesis in
response to NaF. CGP 43187, an inhibitor of the 14 kDa secretory PLA2
(sPLA2), did not affect NaF-induced AA release. However, AACOCF3, a
specific inhibitor of the cytosolic 85 kDa PLA2 (cPLA2), abrogated AA
release and PGI2 production in response to 60 mM NaF. A biphasic
pattern of PGI2 production was also obtained with the GTP-analogs
guanosine 5-O-thiotriphosphate (GTP[gamma]S) and guanylyl
-imidodiphosphate (Gpp(NH)p) in permeabilized BAEC. Pretreatment of
the cells with guanosine 5-O-thiodiphosphate (GDP[beta]S) suppressed
both the inhibition and the stimulation of AA release induced by
Gpp(NH)p. In addition, phenylisopropyl adenosine (PIA) inhibited the
release of AA and PGI2, while ATP and bradykinin increased PGI2.
Pertussis toxin (PTX) not only inhibited both ATP- and bradykinin-
stimulated PGI2 release, but also reversed the inhibitory effect of
PIA, resulting in a significant stimulation. These findings strongly
suggest that in BAEC, cPLA2 is coupled with more than one G protein
that are involved in both inhibition and stimulation of cPLA2
activity.
Received 27 March 1995; accepted in final form 20 February 1996.
APS Manuscript Number C171-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96