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Swelling-Induced Arachidonic Acid Release via the 85-kDa cPLA 2 in Human Neuroblastoma Cells

1998; American Physiological Society; Volume: 79; Issue: 3 Linguagem: Inglês

10.1152/jn.1998.79.3.1441

1522-1598

Srisaila Basavappa, Stine F. Pedersen, Nanna K. Jørgensen, J. Clive Ellory, Else K. Hoffmann,

Marine Toxins and Detection Methods

Basavappa, Srisaila, Stine F. Pedersen, Nanna K. Jørgensen, J. Clive Ellory, and Else K. Hoffmann. Swelling-induced arachidonic acid release via the 85-kDa cPLA 2 in human neuroblastoma cells. J. Neurophysiol. 79: 1441–1449, 1998. Arachidonic acid or its metabolites have been implicated in the regulatory volume decrease (RVD) response after 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 nine minutes of hypo-osmotic exposure the rate of 3 H-arachidonic acid ( 3 H-AA) release increased to 250 ± 19% (mean ± SE, n = 22) as compared with cells under iso-osmotic conditions. This 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 activated during cell swelling. In contrast, preincubation with U73122, an inhibitor of phospholipase C, did not affect the swelling-induced release of 3 H-AA. Swelling-activated efflux of 36 Cl and 3 H-taurine were inhibited after preincubation with AACOCF 3 . Thus the swelling-induced activation of cPLA 2 may be essential for stimulation of both 36 Cl and 3 H-taurine efflux during RVD. As the above observation could result from a direct effect of AA or its metabolite leukotriene D 4 (LTD 4 ), the effects of these agents were investigated on swelling-induced 36 Cl and 3 H-taurine effluxes. In the presence of high concentrations of extracellular AA, the swelling-induced efflux of 36 Cl and 3 H-taurine were inhibited significantly. In contrast, addition of exogenous LTD 4 had no significant effect on the swelling-activated 36 Cl efflux. Furthermore, exogenous AA increased cytosolic calcium levels as measured in single cells loaded with the calcium sensitive dye Fura-2. On the basis of these results we propose that cell swelling activates phospholipase A 2 and that this activation via an increased production of AA or some AA metabolite(s) other than LTD 4 is essential for RVD.