PLATELET MEMBRANE TOPOGRAPHY - COLOCALIZATION OF THROMBOSPONDIN AND FIBRINOGEN WITH THE GLYCOPROTEIN-IIB-IIIA COMPLEX

  • 1 January 1985
    • journal article
    • research article
    • Vol. 66  (4) , 926-934
Abstract
The distribution of platelet thrombospondin (TSP), fibrinogen, and glycoproteins IIb-IIIa (GPIIb-IIIa) and GPlb were studied in resting and activated human platelets using frozen thin-secetion immunoelectron microscopy. In resting platelets, TSP and fibrogen were found within alpha granules and not on the platelet surface. In unstimulated platelts, GPIIb-IIIa and GPlb were distributed diffusely over the platelet membrane as well as within the body of the platelets. Upon thrombin or A23187 stimulation, TSP, fibrinogen, and GPIIb-IIIa colocalized on the platelet membrane and the canalicular system as well as on pseudopodia and between adherent platlets. GPlb distribution was unchanged by platelet activation. The findings support the hypothesis that a macromolecular complex of TSP-fibrinogen and GPIIb-IIa forms on the activated platelet membrane.