S. Basavappa et al., SWELLING-INDUCED ARACHIDONIC-ACID RELEASE VIA THE 85-KDA CPLA(2) IN HUMAN NEUROBLASTOMA-CELLS, Journal of neurophysiology, 79(3), 1998, pp. 1441-1449
Arachidonic acid or its metabolites have been implicated in the regula
tory volume decrease (RVD) response after hypotonic cell swelling in s
ome mammalian cells. The present study investigated the role of arachi
donic acid (AA) during RVD in the human neuroblastoma cell line CHP-10
0. During the first nine minutes of hypo-osmotic exposure the rate of
H-3-arachidonic acid (H-3-AA) release increased to 250 +/- 19% (mean /- SE, n = 22) as compared with cells under iso-osmotic conditions. Th
is release was significantly inhibited after preincubation with AACOCF
(3), an inhibitor of the 85-kDa cytosolic phospholipase A(2) (cPLA(2))
. This indicates that a PLA(2), most likely the 85-kDa cPLA(2) is acti
vated during cell swelling. In contrast, preincubation with U73122, an
inhibitor of phospholipase C, did not affect the swelling-induced rel
ease of H-3-AA. Swelling-activated efflux of 36Cl and H-3-taurine were
inhibited after preincubation with AACOCF(3). Thus the swelling-induc
ed activation of cPLA(2) may be essential for stimulation of both 36Cl
and H-3-taurine efflux during RVD. As the above observation could res
ult from a direct effect of AA or its metabolite leukotriene D-4 (LTD4
), the effects of these agents were investigated on swelling-induced C
l-36 and H-3-taurine effluxes. In the presence of high concentrations
of extracellular AA, the swelling-induced efflux of Cl-36 and H-3-taur
ine were inhibited significantly. In contrast, addition of exogenous L
TD4 had no significant effect on the swelling-activated Cl-36 efflux.
Furthermore, exogenous AA increased cytosolic calcium levels as measur
ed in single cells loaded with the calcium sensitive dye Fura-2. On th
e basis of these results we propose that cell swelling activates phosp
holipase A(2) and that this activation via an increased production of
AA or some AA metabolite(s) other than LTD4 is essential for RVD.