title: Active release of human platelet factor VIII-related antigen by adenosine diphosphate, collagen, and thrombin.
abstract: Platelet Factor VIII-related antigen (VIIIR:Ag) represents a significant proportion of the total circulating VIIIR:Ag pool. However, its participation in the events of primary hemostasis has not been shown. We now report that platelet-contained VIIIR:Ag is released from platelets by collagen, ADP and thrombin. The concentrations of these agonists, required for VIIIR:Ag release, are the same or lower than those required for release of serotonin, lysosomal enzymes, or fibrinogen. This release has the features of an energy-dependent secretory response because it is blocked by the metabolic inhibitors, antimycin A and 2-deoxy-D-glucose. The electrophoretic characteristics of the VIIIR:Ag released by collagen and ADP are similar to those of plasma VIIIR:Ag. However, thrombin-released platelet VIIIR:Ag differs from that of plasma in that the less anodal forms are relatively depleted. These differences do not appear to be the result of proteolytic degradation of platelet-derived VIIIR:Ag, but may reflect interactions between specific molecular forms of VIIIR:Ag and the platelet membrane. These studies suggest mechanisms by which platelet-contained VIIIR:Ag may contribute to the primary events of hemostasis.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology*; D000941:Antigens / Q000032:analysis / Q000276:immunology; D001345:Autoradiography; D001792:Blood Platelets / Q000276:immunology / Q000378:metabolism*; D003094:Collagen / Q000494:pharmacology*; D005169:Factor VIII / Q000276:immunology / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism; D006487:Hemostasis; D006801:Humans; D007122:Immunoelectrophoresis; D013917:Thrombin / Q000494:pharmacology*; D013997:Time Factors; D014842:von Willebrand Diseases / Q000097:blood / Q000378:metabolism
chemical_list: D000941:Antigens; D000244:Adenosine Diphosphate; D005169:Factor VIII; D005340:Fibrinogen; D003094:Collagen; D013917:Thrombin