GPIb-VWF–independent contributions to platelet translocation.

Combined VWF-A1 domain and P-selectin inhibition potently inhibited both translocation and adhesion, indicating that the GPIbα-mediated interactions occurred largely with the VWF-A1 domain. However, the small but significant increment in inhibition when GPIbα was blocked in addition to the VWF-A1 domain leaves some room for alternate high shear-resistant partners of GPIbα besides VWF. GPIIb/IIIa inhibition in addition to VWF-A1 domain blocking also yielded some further inhibition of adhesion, compatible with a role for GPIIb/IIIa-VWF RGD interactions during the adhesion of activated platelets (*P < .05; **P < .01).