Platelet-activating factor (PAF) is the common name given to lO-alkyl-2-acetyl-sn-glycero-3-phospho-choline (Fig. la: also. see refs 14). a biologically active phospholipid. It transmits signals between cells and thus functions in a similar fashion to hormones, cytokines, interleukins. and other signalling molecules. PAF was originally found as a (a) PAF

1-0-alkyl-2-acetyl-srglycero-3-phosphocholine factor released from stimulated rabbit basophils that activates platelets. It was independently identified as an endogenous polar lipid from kidney that lowered blood pressure in experimental animals. It is known now that PAF is produced by a wide variety of isolated human cells. including endothelial cells. polymorphonuclear leucocytes (PMNs). eosinophils. macrophages, monocytes. platelets, mast cells, and spermatozoa. It is also produced by complex adult (bl A PAF-like oxidized phospholipid l-palrnitoyl-2-[5-oxovaleroyll-srglycero-3-phosphocholine