A role for pkc[epsilon] and map kinase in bradykinin-induced
arachidonic acid release in rabbit ccd cells.
Lal, Mark A., Pierre R. Proulx, and Richard L. H[acute]ebert.
Departments of Cellular and Molecular Medicine, Biochemistry, and
Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario,
Canada, K1H 8M5
APStracts 5:0012F, 1998.
Arachidonic acid (AA) release is the rate limiting step in the
production of prostaglandins, an important class of
autocrine/paracrine factors that modulate collecting duct function.
Previous results from this laboratory have established cytosolic
phospholipase A2 (cPLA2) as the enzyme responsible for bradykinin
(BK)-stimulated AA mobilization in rabbit cortical collecting duct
(RCCD) cells and the present study pursues the intracellular
signalling mechanisms responsible for its activation. Pretreatment of
cells with Ro31-8220, an inhibitor of protein kinase C (PKC), or
PD98059, an inhibitor of the mitogen-activated protein kinase (MAPK)
cascade, resulted in a 50-60% reduction in BK-stimulated AA release.
Incubation of RCCD cells with a combination of both Ro31-8220 and
PD98059 did not achieve a greater inhibition of either BK-stimulated
AA release or cPLA2 activity, possibly indicating that MAPK
activation was dependent upon prior activation of PKC. This was
supported by the observation that BK-induced MAPK activation could be
reversed by either inhibitor. Additional experiments dealing with
immunoblots for PKC isozymes revealed that RCCD cells express PKC
species [alpha], [delta], [epsilon], and H. Following BK stimulation,
only PKC[epsilon] translocated to the particulate fraction. Based on
these results, it appears that PKC is activated and involved in the
sequential activation of MAPK and cPLA2 following BK treatment. The
results also suggest that PKC[epsilon] may be the isozyme implicated
in the process.
Received 23 July 1997; accepted in final form 7 January 1998.
APS Manuscript Number F243-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 28 January 1998