The role of phospholipases a2, c and d in the bradykinin-induced
release of arachidonic acid in mdck cells.
Kennedy, Chris R. J., Pierre R. Proulx, and Richard L. H[acute]ebert.
Departments of Biochemistry and Physiology, Faculty of Medicine,
University of Ottawa, Ottawa, Ontario, Canada, K1H 8M5
APStracts 3:0143C, 1996.
The role of cytosolic phospholipase A2 (cPLA2), phosphatidylcholine
-specific phospholipase C (PC-PLC) and phospholipase D (PLD) in the
bradykinin (BK)-stimulated release of arachidonic acid (AA) was
examined in MDCK cells. Release of AA, phosphorylcholine, choline and
phosphatidic acid (PA) or the transphosphatidylation product,
phosphatidylethanol (PEt) was detected after 1 min of BK stimulation.
A role for PC-PLC was confirmed with D609, which reduced BK
-stimulated AA by 70%. Ethanol, which blunts PA formation, diminished
BK-stimulated AA release by 50%. Together, D609 and EtOH inhibited
this release almost completely. Evidence indicated that DAG and PA
can enhance PLA2 activity when added to cytosol extracts. The enzyme
responsible for AA release was characterized as cPLA2 since PLA2
activity assayed in cell extracts was largely inhibited by an
antibody to this enzyme. The membrane fraction PLA2 activity
increased significantly in BK-stimulated cells. We conclude that BK
-signalling in MDCK cells is mediated by the lipid products of PC-PLC
and PLD, increasing cPLA2 activity, possibly by causing perturbations
in the bilayer structure of its substrate, by a direct effect on the
enzyme or by activation of protein kinases such as PKC.
Received 12 March 1996; accepted in final form 23 April 1996.
APS Manuscript Number C137-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96