The effect of adsorbed fibrinogen, fibronectin, von Willebrand factor and vitronectin on the procoagulant state of adherent platelets

Procoagulant (activated) platelets provide a site for assembly of the proth rombinase complex which can rapidly convert prothrombin into thrombin (a po tent inducer of clot formation). Previously, we reported that adhesion of p latelets to surfaces preadsorbed with blood plasma caused them to become pr ocoagulant. In the present study we investigated the effect of adsorbed adh esion proteins (fibrinogen (Fg), fibronectin (Fn), von Willebrand factor (v WF) and vitronectin (Vn)) on the procoagulant activity of adherent platelet s. Adsorbed Fn, vWF and Fg promoted platelet adhesion in the following orde r: Fn < vWF = Fg. However, these proteins promoted platelet activation (thr ombin generation per adherent platelet) in the following order: Fg < Fn < v WF. Adsorption with a series of dilutions of normal plasma, serum, and plas mas deficient in or depleted of von Willebrand factor (de-vWF), fibronectin (de-Fn), vitronectin (de-Vn), or both vitronectin and fibronectin (de-VnFn ) resulted in varied platelet adhesion, but little difference in platelet a ctivation. However, preadsorption with dilute de-vWF plasma induced lower p rocoagulant activity than normal plasma. Preadsorption with normal plasma r esulted in higher levels of platelet activation than preadsorption with Fg, suggesting that adsorption of plasma proteins other than Fg caused the hig h levels of activation observed for plasma preadsorbed surfaces. (C) 2000 E lsevier Science Ltd. All rights reserved.