A SIMPLE AND PRECISE METHOD FOR THE ROUTINE DETERMINATION OF PLATELET-ACTIVATING-FACTOR IN BLOOD AND URINE

A simple and precise method is described for the measurement of platel et-activating factor (PAF) in blood and urine. The method involves the isolation of PAF from blood samples by two successive steps. In the f irst step, blood proteins are precipitated with ethanol and the ''free '' PAF, i.e., the PAF which is extractable with ethanol, is recovered. In the second step,''bound'' PAF, i.e., PAF not extractable with etha nol, is extracted from the protein precipitate with chloroform/methano l/ water. The extraction of PAF from urine samples requires only the e thanol extraction step. ''Free'' and ''bound'' PAF are then each fract ionated by silicic acid column chromatography, and the methanol/water eluent containing PAF is then further fractionated by highperformance liquid chromatography using an isocratic solvent system of acetonitril e/methanol/water. PAF is then quantitated by measuring its ability to induce platelet aggregation in an aggregometer. Application of the met hod to blood and urine samples from twentythree healthy volunteers rev ealed PAF levels in blood of 140-480 pg/mL (630-254.4 pg ''free'' PAF/ mL and 64-225.6 pg ''bound'' PAF/mL), and of 1.2-4.0 pg PAF/mL in urin e. The method overcomes various technical problems and was shown to be very precise. It should prove useful for monitoring PAF levels in var ious disease conditions.