ARACHIDONIC-ACID MOBILIZATION IN P388D(1) MACROPHAGES IS CONTROLLED BY 2 DISTINCT CA2-DEPENDENT PHOSPHOLIPASE A(2) ENZYMES()

Macrophage-like P388D(1) cells mobilize arachidonic acid (AA) and prod uce prostaglandin E(2) upon stimulation with bacterial lipopolysacchar ide and platelet-activating factor. We have now demonstrated that AA m obilization in these cells is composed of two distinct events: a trans ient phase in which AA accumulates in the cell and a sustained phase i n which the fatty acid accumulates in the incubation medium. Both phas es are markedly dependent on the presence of Ca2+ in the extracellular medium. Treatment with an antisense oligonucleotide to group II phosp holipase A(2) inhibits the accumulation of AA in the incubation medium , but has no effect on the accumulation of this fatty acid in the cell . In addition, treatment with antisense oligonucleotide to group II ph ospholipase A(2) has no effect on the uptake of the esterification of AA. Collectively, these results indicate that, in addition to the prev iously demonstrated role of group II phospholipase A(2) in AA mobiliza tion in activated P388D(1) cells, another phospholipase A(2), distinct from the group II enzyme, is implicated in raising the levels of intr acellular AA during the early steps of P388D(1) cell activation and in modulating deacylation/reacylation reactions involving AA. The data s uggest that each of the different phospholipase A(2) enzymes present i n P388D(1) cells serves a distinct role in cell function.