Synthesis of the 1-O-hexadecyl molecular species of platelet-activating factor by airway epithelial and vascular endothelial cells.

Epithelial and endothelial cells may regulate leukocyte adherence and influx into underlying tissue, and this regulatory function may be based on the synthesis of leukocyte chemotaxins by these cells. We have measured the production of the potent lipid autocoid, platelet-activating factor (PAF) by airway epithelial and vascular endothelial cells using stable isotope dilution negative-ion chemical-ionization mass spectrometry. Both primary cultures of airway epithelial cells isolated from human and ovine tracheal mucosa and cultures of human umbilical vein endothelial cells generated measurable amounts of PAF under basal culture conditions and significantly increased amounts upon stimulation with ionophore A23187. The 1-O-hexadecyl molecular species of PAF was much more abundant than the 1-O-octadecyl species in each of these cell populations. The results suggest a possible common biochemical mechanism for regulation of inflammatory cell influx into tissues by barrier cells in epithelium and endothelium.