STIMULATION OF ARACHIDONIC-ACID RELEASE FROM SWISS 3T3 CELLS BY RECOMBINANT BASIC FIBROBLAST GROWTH-FACTOR - INDEPENDENCE FROM PHOSPHOINOSITIDE TURNOVER

In this study we have attempted to characterize the mechanism of recom binant bovine basic fibroblast growth factor (rbFGF)-induced release o f arachidonic acid from prelabelled Swiss 3T3 fibroblasts. Recombinant bFGF caused the release of [H-3]arachidonic acid from metabolically l abelled cells in a dose- and time-dependent manner. This effect was ma ximal with 10 ng rbFGF/ml and became significant after a 30-min incuba tion. Although rbFGF was able to cause a modest increase in total inos itol phosphate accumulation, an examination of the time-course of the latter effect revealed that enhanced [H-3]arachidonic-acid release cou ld not have been derived from phosphoinositide metabolism. Evidence su ggesting that rbFGF-induced release of [H-3]arachidonic acid was being mediated via a PLA(2) pathway was obtained by pharmacological antagon ism using mepacrine, a putative PLA(2) inhibitor. Moreover, treatment of cells with neomycin failed to attenuate rbFGF-mediated release of [ H-3]arachidonic acid. Chelation of extracellular calcium by EGTA was f ound to abrogate rbFGF-induced liberation of [H-3]arachidonic add Down -regulation of protein kinase C (PKC) by prolonged treatment of cells with the phorbol ester, PMA, was observed to have no effect on the act ion of rbFGF on [H-3]arachidonic add release from Swiss 3T3 fibroblast s. While rbFGF was found to cause the indomethacin-sensitive productio n of prostaglandin E(2) (PGE(2)) in a dose-dependent manner, this effe ct was independent of rbFGF-induced reinitiation of DNA synthesis. Cle arly, the effect of rbFGF on cellular DNA synthesis was being mediated independently of PGE(2) biosynthesis. We discuss the potential import ance of the PLA(2)-signalling pathway in the mechanism of action of fi broblast growth factors.