Summary
The present report describes the in vitro inhibition of prothrombin consumption by lipid extracted from normal human platelet-poor
plasma. Pro-coagulant lipids and the test plasma lipids were dissolved in the same
solvent and evaporated to dryness. The dried lipid mixture was emulsified in platelet-poor
plasma, and the plasma clotted by recalcification. Inhibition of prothrombin consumption
by plasma lipid was observed when the ratio of plasma lipid to procoagulant lipid
equaled or exceeded 5:1. The inhibitory effect of plasma lipid on prothrombin consumption
was not observed when procoagulant activity was provided by intact platelets or platelet
granules.
Human plasma lipids have been fractionated on silicic acid columns to permit identification
of the plasma lipid component responsible for the inhibition of prothrombin consumption.
The inhibitory activity is present in a lipid fraction which is 95% lecithin. Other
plasma lipid components exhibit little or no inhibitory activity.
