Activation of Phospholipid Thromboplastin by Lecithin

Abstract

THIS communication is prompted by the recent report of Newlands and Wild¹ that a preparation of soybean phospholipid can serve as a useful source of platelet factor for the thromboplastin generation test. We have been trying in this laboratory for several years to define the phospholipid structures responsible for thromboplastic activity. Reports have been limited to preliminary communications^2–4 because the degree of purity of the active fractions does not permit a rigorous correlation of structure with activity, although the evidence suggests that the essential structural requirement is the presence of a serine or ethanolamine base in a glycerophospholipid molecule. It should be noted that the activity discussed in this communication is acceleration of the conversion of prothrombin to thrombin in the presence of calcium and a suitable (glass) surface in mammalian coagulation systems. Phosphatidyl serine, which has a higher activity per unit weight than thromboplastic protein in accelerating prothrombin conversion in the rabbit system², is without effect when studied with avian plasmas.