Platelet-activating factor may act as a second messenger in the release of icosanoids and superoxide anions from leukocytes and endothelial cells

Abstract

Platelet-activating factor (PAF) is generated by endothelial cells, polymorphonuclear leukocytes, and macrophages after activation by appropriate receptor agonists, but much of the PAF remains intracellular. We have investigated whether PAF formation is important for the subsequent generation of icosanoids and superoxide anions by these cells. The generation of prostacyclin and leukotriene B4 were measured by radioimmunoassay, superoxide anion was measured by reduction of cytochrome c, and PAF was measured by bioassay. In each cell type, PAF formation preceded or accompanied icosanoid generation. Bradykinin-induced prostacyclin generation in endothelial cells was markedly reduced by the PAF ..