The role of fibronectin in platelet adhesion to plasma preadsorbed polystyrene

Platelet adhesion to synthetic surfaces that come in contact with blood is mediated by the adsorption of adhesive plasma proteins, especially fibrinog en. However, the roles of other adhesive proteins, such as fibronectin, vit ronectin: and von Willebrand factor in platelet adhesion are not yet clear. In this study, the role of fibronectin in platelet adhesion to surfaces wa s assessed using three approaches. First, platelet adhesion was measured on Immulon I(R) preadsorbed with fibronectin-depleted plasma or fibronectin-d epleted plasma replenished with increasing amount of fibronectin. Under the se conditions, fibronectin adsorbed from plasma did not have any effect on platelet adhesion, while fibrinogen played a major role in mediating platel et adhesion. Since fibronectin might play a role in platelet adhesion to su rfaces which adsorb little or no fibrinogen; we also used two other strateg ies to assess the potential role of fibronectin. One was to use platelets t reated with a platelet activation inhibitor, prostaglandin E-1, which preve nts the activation of platelet fibrinogen receptor GP IIb/IIIa. The adhesio n of prostaglandin E-1-treated platelets to Immulon IO preadsorbed with pla sma was greatly decreased compared to that of untreated platelets, but was increased by the addition of supernormal concentrations of fibronectin to t he plasma. This suggests that GP Ic/IIa, rather than GP IIb/IIIa, might be the platelet receptor which is responsible for platelet adhesion to surface -bound fibronectin. Finally, we studied the effect of fibronectin on platel et adhesion to surfaces preadsorbed with fibronectin-depleted afibrinogenem ic plasma. We found that fibronectin re-addition to fibronectin-depleted af ibrinogenemic plasma increased platelet adhesion. However. our most importa nt Ending was that fibronectin seems to play little or no role is mediating platelet adhesion to polystyrene surfaces preadsorbed with normal plasma.