Platelet Phosphatides: Their Separation, Identification, and Clotting Activity1

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Abstract
Acetone dried, chloroform extracted human blood platelets were subjected to chromatography on silicic acid impregnated paper and silicic acid columns. On paper, 3 solvent systems were used. Best resolution was obtained using diisobutyl ketone: acetic acid: water (40:25:5 v/v/v). Five components were noted and identified as phos-phatidylethanolamine, phosphatidylserine, lecithin, sphingomyelin and inositol phosphatide. Eluates from papers did not show thromboplastic activity. Platelet extract was eluted from a silicic acid column with ether and methanol. The ether eluates contained non-phospholipids and the methanol eluates consisted of phospholipids which had thromboplastic activity. Phosphatidylserine in small amounts could replace platelets in the thromboplastin generation and prothrombin consumption tests. The phosphatidylethanolamine fractions had clotting activity, but contained phosphatidylserine, thus its role could not be clarified. Lecithin and sphingomyelin had no activity. A late fraction, which contained no N and had the chromatographic properties of phosphatidic acid showed coagulation activity. At high concentrations the active phosphatides showed anticoagulant properties, which is also the case with intact platelets.