title: The procoagulant activity of partial thromboplastin extracts: the role of phosphatidyl serine.
abstract: The role of phosphatidyl serine (PS) in the procoagulant activity of the APTT test has been studied further, using extracts of improved purity derived from a combination of high performance liquid chromatography and thin layer chromatography. The central role of PS in the APTT has been confirmed but the anticoagulant effect described in our previous report has been localised to contamination with phosphatidyl inositol (PI). A comparatively weak procoagulant activity was detected in purified PI- and lyso PS-containing liposomes and the former had an inhibitory action in mixtures diluted to less than 1 microgram/litre. This was enhanced by the presence of PS in combination experiments. Some correlation was noted between the degree of unsaturation of test liposomes and their procoagulant activity. The observations suggest that PS has a precise and unique role in the procoagulant activity expressed in this test system. PS possesses a strong negative charge and has two fatty acid groups. Other negatively charged phospholipids in this test system were less active. It appears, therefore, that the packing of PS into the lipid bilayer, which depends upon the length and degree of unsaturation of its fatty acid groups, is of considerable importance in establishing the surface topography essential for optimal procoagulant activity. Knowledge of the role played by various phospholipids in the procoagulant activity of the APTT reagent should enable improved standardisation and quality control in the future.
mesh_terms: D001777:Blood Coagulation / Q000187:drug effects; D001780:Blood Coagulation Tests; D005227:Fatty Acids / Q000494:pharmacology; D006801:Humans; D010718:Phosphatidylserines / Q000302:isolation & purification / Q000502:physiology*; D013925:Thromboplastin / Q000032:analysis*
chemical_list: D005227:Fatty Acids; D010718:Phosphatidylserines; D013925:Thromboplastin