BASIC FGF ACTIVATES PHOSPHOLIPASE-D IN ENDOTHELIAL-CELLS IN THE ABSENCE OF INOSITOL-LIPID HYDROLYSIS

In the absence of inositol-lipid hydrolysis, mitogenic concentrations of basic fibroblast growth factor (bFGF) stimulated phosphatidylbutano l formation in the presence of butan-1-ol in [H-3]myristate-labeled hu man umbilical vascular endothelial (HUVE) cells, indicating that the f ibroblast growth factor receptor was able to couple to the activation of phospholipase D (PLD). The ability of bFGF and 12-O-tetradecanoylph orbol-13-acetate (TPA) to stimulate PLD activity was completely abolis hed in cells pretreated with 400 nM TPA for 48 h to downregulate prote in kinase C (PKC). bFGF-stimulated PLD activity was inhibited by genis tein (5 mu M; P < 0.02) and the PKC inhibitor 1-(5-isoquinolinylsulfon yl)-2-methylpiperazine (H-7, 5 mu M; P < 0.001) as well as by the remo val of calcium from extracellular environment. bFGF induced DNA synthe sis in a dose-dependent manner, and pretreatment of cells with H-7 inh ibited the mitogenic activity of bFGF. These results indicate that act ivation of PKC is responsible for bFGF-induced PLD activation and the mitogenic activity of bFGF in HUVE cells. A coupled PLD/3-sn-phosphati date phosphohydrolase pathway may play a role in the regulation of end othelial cell proliferation.