Interleukin-1[beta] stimulates phospholipase a2 activity in adult
rat ventricular myocytes.
McHowat, Jane, and Shi Liu.
Department of Pathology and Department of Medicine, Division of
Cardiology, University of Arkansas for Medical Sciences
APStracts 3:0278C, 1996.
We have examined whether interleukin 1[beta] (IL-1[beta]) modulates
phospholipase A2 (PLA2) activity in ventricular myocytes. PLA2
activity was measured in isolated membrane and cytosol fractions
using (16:0,[3H]18:1) plasmenylcholine and phosphatidylcholine in the
absence and presence of Ca. When measured in the absence of Ca using
plasmenylcholine, exposure to 5 ng/ml IL 1[beta] caused an increase
in membrane associated PLA2 activity for 10 min that returned to
basal levels by 20 min. In the presence of Ca using
phosphatidylcholine, IL 1[beta] had no effect on membrane-associated
PLA2 but decreased cytosolic PLA2 activity. Additionally, IL 1[beta]
caused an increase in arachidonic acid release in 20 min.
Pretreatment with E 6 (bromomethylene)tetrahydro 3 (1-naphthalenyl)
2H pyran 2 one, a selective Ca independent PLA2 inhibitor, blocked IL
1[beta] induced increases in both PLA2 activity and arachidonic acid
release. Exposure to IL-1 receptor antagonist (IL 1ra) alone had no
effect on membrane-associated PLA2 activity. When incubated with IL
-1[beta], IL-1ra inhibited the IL 1[beta]-enhanced PLA2 activity.
These results show that via activation of its receptors, IL 1[beta]
stimulates specifically membrane-associated, Ca- independent,
plasmalogen-selective PLA2 in rat ventricular myocytes.
Received 17 July 1996; accepted in final form 26 August 1996.
APS Manuscript Number C395-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996