Dissociation of the Factor-VIII complex during clotting: role of thrombin and phospholipids.
To study the dissociation of the two moieties of the factor-VIII complex during clotting, plasma, concentrate and serum were chromatographed on 4% agarose. In plasma and concentrate factor-VIII coagulant activity (VIII C), factor-VIII coagulant antigen (VIII C:Ag), and factor-VIII-related antigen (VIII R:Ag) eluted together in the void volume, but some VIII C:Ag eluted after the void volume. The amount of VIII C:Ag eluting after the void volume was made smaller by adding proteinase inhibitors. In serum nearly all VIII C:Ag eluted after the void volume. From factor-VIII complex immunoadsorbed by means of an antibody against VIII R:Ag no VIII C:Ag was dissociated by thrombin or by thrombin and physiologic CaCl2 concentrations. Radiolabelled human thrombin did not bind to the VIII C:Ag of immunoadsorbed factor-VIII complex. VIII C:Ag displaying VIII C was dissociated from immunoadsorbed factor-VIII complex by human brain thromboplastin or by phosphatidyl-serine. Our results suggest that VIII C:Ag and VIII R:Ag dissociate during clotting. This dissociation seems not to be mediated by thrombin, but may be mediated by phospholipids.
D000941:Antigens / Q000378:metabolism; D001780:Blood Coagulation Tests; D002850:Chromatography, Gel; D005169:Factor VIII / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D010743:Phospholipids / Q000502:physiology*; D013917:Thrombin / Q000502:physiology*; D014841:von Willebrand Factor
D000941:Antigens; D010743:Phospholipids; D014841:von Willebrand Factor; D005169:Factor VIII; D013917:Thrombin