THE MEMBRANE GLYCOPROTEIN IIB IIIA COMPLEX MEDIATES DEPOSITION OF THROMBIN-STIMULATED BLOOD-PLATELETS ON POLYSTYRENE PLASTIC UNDER STATIC CONDITIONS/

A major challenge in the use of artificial materials for implant devic es, artificial organs, and extra-corporeal circulation systems, is the adhesion of platelets and the subsequent formation of platelet aggreg ates on the non-biological surface. The mechanism of platelet attachme nt to artificial surfaces is not completely understood. Using an enzym e immunoassay, we examined platelet deposition to the polystyrene plas tic of microtiter plate wells under static conditions. Following throm bin stimulation, platelets adhered to the wells. This adhesion process was suppressible by the use of different substances known to interfer e with the function of the platelet surface glycoprotein IIb/IIIa comp lex (GPIIb/IIIa). The substances we used were: ethylenediaminetetraace tic acid (EDTA), tetrapeptide RGDS (Arg-Gly-Asp-Ser), and a monoclonal antibody directed against the ma moiety of the GPIIb/IIIa complex. Ou r results indicate that the GPIIb/IIIa complex is the platelet recepto r which mediates platelet adhesion to polystyrene plastic under such s tatic conditions. The GPIIb/IIIa complex should consequently be regard ed as a multifunctional platelet regulator which, depending on the cir cumstances, may support platelet adhesion as well as platelet aggregat ion. By contrast, a monoclonal antibody directed against the platelet surface glycoprotein complex Ib/IX (GPIb/IX) did not under the same st atic conditions inhibit platelet deposition to the polystyrene plastic . In the microtiter wells, platelet alpha-granular proteins were detec ted either on the surface of adherent platelets or, when platelet depo sition was inhibited by EDTA directly on the polystyrene plastic. In t he latter case, fibrinogen and thrombospondin were definitely the domi nating proteins. The presence of platelet-derived proteins in the micr otiter wells significantly enhanced the adhesion of thrombin-stimulate d platelets but not of non-stimulated platelets.