Complex formation of platelet thrombospondin with fibrinogen.

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Abstract

Using an enzyme-linked immunosorbent assay, we have demonstrated that purified human fibrinogen forms a complex with adsorbed platelet thrombospondin. The formation of the fibrinogen-thrombospondin complex was specific, saturable, and partially inhibited by mannosamine, glucosamine, and arginine. These same inhibitors have been previously shown to block thrombin-induced platelet lectin activity and platelet thrombospondin lectin activity. Adsorbed thrombospondin also formed a complex with fibronectin, although the extent of complex formation was significantly less than the extent of formation of the fibrinogen-thrombospondin complex. Platelet membrane glycoproteins IIb and IIIa, which have been previously shown to bind fibrinogen, did not inhibit the formation of the fibrinogen-thrombospondin complex. The present study supports the hypothesis that the interaction of fibrinogen with thrombospondin on the activated platelet surface may be an important step in the platelet aggregation process.

Authors

L L Leung, R L Nachman