PLATELET-ADHESION TO MULTIMERIC AND DIMERIC VON-WILLEBRAND-FACTOR ANDTO COLLAGEN TYPE-III PREINCUBATED WITH VON-WILLEBRAND-FACTOR

As part of a systematic study of platelet interaction with adhesive pr oteins under flow conditions, we studied platelet adhesion to multimer ic and dimeric von Willebrand factor (vWF) coated to glass. vWF-depend ent adhesion to collagen type III was studied for comparison. Adhesion to glass-coated vWF and vWF-mediated adhesion to collagen type III we re in many respects similar. Both showed no decrease al increasing she ar rates and a decline to 50% of maximum with a low-molecular-weight m ultimeric fraction. Adhesion to glass-coated vWF was partially inhibit ed by heparin and completely inhibited by prostaglandin I, and anti-gl ycoprotein (GP) Ib and anti-GPIIb-IIIa antibodies. vWF-dependent adhes ion to collagen was not inhibited by heparin, was partially inhibited by anti-GPIIb-IIIa, and was completely inhibited by prostaglandin I-2, and anti-GPIb. Recombinant dimeric vWF was made by deletion of the pr opeptide and expression in Chinese hamster ovary cells. Adhesion was 5 0% of that with plasma vWF, and larger concentrations of dimeric vWF w ere required. Adhesion to dimeric vWF was optimal at 1500 s(-1), with a gradual decrease at higher shear rates. We conclude that adhesion to collagen type III is strongly but not completely determined by the ad hesive properties of vWF.