Summary
We have employed synthetic peptides with sequences corresponding to the integrin receptor-recognition
regions of fibrinogen as inhibitors of platelet aggregation and adhesion to fibrinogen-and
fibrin-coated surfaces in flowing whole blood, using a rectangular perfusion chamber
at wall shear rates of 300 s–1 and 1,300 s–1. D-RGDW caused substantial inhibition of platelet aggregation and adhesion to fibrinogen
and fibrin at both shear rates, although it was least effective at blocking platelet
adhesion to fibrin at 300 s–1. RGDS was a weaker inhibitor, and produced a biphasic dose-response curve; SDRG was
inactive. HHLGGAK-QAGDV partially inhibited platelet aggregation and adhesion to fibrin(ogen)
at both shear rates. These results support the identification of an RGD-specific receptor,
most likely the platelet integrin glycoprotein IIb: III a, as the primary receptor
responsible for platelet: fibrin(ogen) adhesive interactions under flow conditions,
and indicate that platelet adhesion to surface bound fibrin(ogen) is stabilized by
multivalent receptor-ligand contacts.