Studies on blood platelet phospholipids*

Abstract

Column chromatography on silicic acid was carried out on phospholipids from acetone-dried, chloroform-extracted human blood platelets. Fractions recovered had the following components : Phosphatidylethanolamine (PE) plus phosphatidylserine (PS) plus inositol phosphatide, PE plus PS, lecithin plus sphingomyelin, and PS alone. Eluates containing only phosphatidylethanolamine and phosphatidylserine were rechromatographed to obtain more complete separation. The resulting fractions appeared to contain one component, but on hydrolysis of these materials it was apparent that each was still contaminated with small amounts of the other. However, on high dilution of each of these mixtures, blood thromboplastin formation was promoted; this suggested that both PE and PS could act as platelet thromboplastic factor in vitro. Inhibitory activity was not noted. The presence of choline phosphatides in the fractions resulted in loss of activity. Plasmalogens were identified and estimated to comprise 23 per cent of total platelet cephalins. They were more closely associated with phosphatidylethanolamine than phosphatidylserine. Lysolecithin could not be detected in the mixed platelet extract or the separated fractions.