Co-adsorbed fibrinogen and von Willebrand factor augment platelet procoagulant activity and spreading

Previously we observed that platelets adherent to surfaces preadsorbed with blood plasma exhibited 1.3 to 2.4 times greater procoagulant activity than platelets on surfaces adsorbed with fibrinogen (Fg) only. These observatio ns suggested that the adhesion proteins adsorbed from plasma may activate p latelets in a cooperative, or synergistic manner. In the present stud?;, po lystyrene surfaces adsorbed with both Fg and VWF induced up to three times greater procoagulant activity than surfaces adsorbed with Fg or VWF only. T he amounts of Fg and VWF adsorbed from binary mixtures that resulted in inc reased procoagulant activity were found to be similar to the amounts that a dsorbed to PS from 100% plasma. The effect of adsorbed adhesion proteins on platelet spreading was also inv estigated. The proportion of fully spread platelets increased, depending on the adhesion protein preadsorbed to the surface, in the following order: V WF < Fg < Fn < (VWF + Fg) < Vn < plasma.