Evidence That Fibrin a-Chain RGDX Sequences Are Not Required for Platelet Adhesion in Flowing Whole Blood

The role of the RGDX putative receptor-recognition sites, which are present on the a chains of fibrin, in promoting platelet adhesion has been examined in flowing whole blood using the rectangular perfusion chamber at wall shear rates of 340 and 1,8oo/s. Platelets adhered to a comparable extent to surfaces coated with native fibrin and surfaces coated with fragment X-fibrin, a product of limited fibrinolysis that lacks the RGDS sites normally present at positions 572 to 575 of the a chains. The strengths of these adhesive interactions were comparable based on the concentrations of the antiadhesive peptide D-RGDW required to block platelet deposition to native and fragment X-fibrin at both low and high wall shear rate. Blocking either or both RGDX sequences with peptidespecific monoclonal antibodies did not inhibit platelet deposition in perfusion experiments per-