[Is there a correlation between sugar content, thrombocyte aggregating activity and molecular size of factor VIII?]

Human and bovine factor VIII, isolated from cryoprecipitates of fresh plasma by gel filtration on Sepharose CL-2B, gave similar elution patterns and showed comparable distribution of oligomers on SDS agarose electrophoretic gels. The carbohydrate content of individual factor VIII bands, measured by reaction with dansyl hydrazine or binding of glucose/mannose specific concanavalin A, was not directly related to the size or von Willebrand activity of factor VIII oligomers. Staining of disulfide-reduced factor VIII subunits, in polyacrylamide gels, with galactose-specific fluorescein-labelled Ricinus communis lectins, showed an increased binding affinity with increasing size and von Willebrand activity of the parent factor VIII. The von Willebrand activity was strongly inhibited by reaction with Ricinus RCAI lectin, whereas concanavalin A inhibited platelet aggregation only at concentrations above 1 mg/ml. These results suggest that galactose residues are involved in the aggregation of platelets by factor VIII.