Platelet-activating factor biological responses

Platelet-activating factor or l-alkyl-2-acetyl- n-glycero-3-phosphocholine is an ether analog of phosphatidylcholine. This biologically active lipid is of great current interest. Initially, it was found to affect aggregation of platelets and to induce a hypertensive response at very low concentrations. Recent research has revealed its role as a mediator of inflammation and of other physiologic effects on many different types of cells. 

In 1979, the chemical structure of PAF was identified as l-alkyl-2-acetyl-sn-gIycero-3-phosphocholine (Fig. 2) (D.J. Hanahan, 1979 M.L. Blank, 1979 J. Benveniste, 1979). The semi-synthetic preparation tested in these initial experiments aggregated platelets at concentrations as low as 10 " M and induced an anti-hypertensive response when as little as 60 ng were administered intravenously to hypertensive or normotensive rats. Threshold concentrations vary by cell type and organism, but PAF can activate human inflammatory cells at concentrations as low as 10 M. PAF induces diverse biological responses (Table 1) and has been implicated as a contributing factor in the pathogenesis of such diverse disease processes as asthma, hypertension, allergies, inflammation, and anaphylaxis. 

---