 Measurement of plasma Lp-PLA2 activity Lp-PLA2 activity in total plasma, in apo B-depleted plasma, after the sedimentation of all apo B-containing lipoproteins with dextran sulfate-magnesium chloride HDL-Lp-PLA2 activity as well as in lipoprotein subfractions, will be determined by the trichloroacetic acid precipitation procedure using 3H-platelet-activating factor PAF 100 μM final concentration as a substrate.16 The reaction will be performed for 10 min at 37C and Lp-PLA2 activity will be expressed as nmol PAF degraded per min per ml of plasma or mg of LDL subfraction protein. The non-HDL-Lp-PLA2 activity will be calculated by subtracting the HDL-Lp-PLA2 activity from the total plasma enzyme activity. Lp-PLA2 specific activity will be expressed as a ratio of the enzyme activity to the enzyme mass nmolngmin. 