The Roles of von Willebrand Factor and Factor VI11 in Arterial Thrombosis: Studies in Canine von Willebrand Disease and Hemophilia A

We have studied the roles of von Willebrand factor (vWF) and factor Vlll in arterial thrombosis in four canine phenotypes: normal (n = 6). hemophilia A (n = 1 l ) , von Willebrand disease (vWD) (n = S), and hemophilia A/vWD (n = 1). vWF activity was determined by botrocetin-induced agglutination of fixed human platelets and vWF antigen (vWF:Ag) by Laurel1 electroimmunoassay and crossed immunoelectrophoresis. Plasma from normal dogs and those with hemophilia A had vWF activity, vWF:Ag, and a full range of vWF:Ag multimers on gel electrophoresis equivalent to normal canine plasma pool. Platelet cytosol contents were isolated by freezing and thawing, triton X-1 00 solubilization, or sonication of washed platelets with and without protease inhibitors and inhibitors of platelet activation. Washed platelets were also stimulated with calcium ionophore and MgCI2. There was no measurable vWF activity or vWF:Ag in platelet lysates or releasates in any dog regardless of phenotype. All dogs were studied using a