SWELLING-INDUCED ARACHIDONIC ACID RELEASE via THE 85 kDa cPLA2 IN HUMAN
NEUROBLASTOMA CELLS.
Srisaila Basavappa, Stine F. Pedersen, Nanna K. Jorgensen, J. Clive Ellory and
Else K. Hoffmann.
University Laboratory of Physiology, University of Oxford, Oxford OX1 3PT,
August Krogh Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark,
Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA
02115.
APStracts 4:0324N, 1997.
ABSTRACT
Arachidonic acid or its metabolites have been implicated in the regulatory
volume decrease (RVD) response following hypotonic cell swelling in some
mammalian cells. The present study investigated the role of arachidonic acid
(AA) during RVD in the human neuroblastoma cell line CHP-100. During the first
9 minutes of hypoosmotic exposure the rate of 3H-arachidonic acid (3H-AA)
release increased to 250 + 19% (n=22) as compared to cells under isoosmotic
conditions. This release was significantly inhibited after preincubation with
AACOCF3, an inhibitor of the 85 kDa cytosolic phospholipase A2 (cPLA2). This
indicates that a PLA2, most likely the 85 kDa cPLA2 is activated during cell
swelling. In contrast, preincubation with U73122, an inhibitor of
phospholipase C, did not affect the swelling-induced release of 3H-AA.
Swelling-activated efflux of 36Cl and 3H-taurine were inhibited following
preincubation with AACOCF3. Thus, the swelling-induced activation of cPLA2 may
be essential for stimulation of both 36Cl and 3H-taurine efflux during RVD. As
the above observation could result from a direct effect of AA or its
metabolite leukotriene D4 (LTD4), the effects of these agents were
investigated on swelling-induced 36Cl and 3H-taurine effluxes. In the presence
of high concentrations of extracellular AA, the swelling-induced efflux of
36Cl and 3H-taurine were inhibited significantly. In contrast, addition of
exogenous LTD4 had no significant effect on the swelling-activated 36Cl
efflux. Furthermore, exogenous AA increased cytosolic calcium levels as
measured in single cells loaded with the calcium sensitive dye Fura-2. Based
on these results we propose that cell swelling activates phospholipase A2, and
that this activation via an increased production of AA or some AA
metabolite(s) other than LTD4 is essential for RVD.
Received 15 July 1997; accepted in final form 13 November 1997.
APS Manuscript Number J589-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 December 1997