Shear stress dependence of VWF self-association. A total of 30 × 106 platelets/mL was subjected to a range of shear rates with 10 μg/mL pVWF-FITC and 60 μg/mL 7E3, either in the presence or absence of 10 μg/mL unlabeled pVWF. A total of 1.5% wt/vol dextran was added in some cases to double media viscosity. Platelets withdrawn at 4 minutes were incubated with CD31-PE and annexin-PE/Cy5 before cytometry analysis. (A) VWF-FITC binding to platelets. (B) Platelet activation. pVWF binding to platelets and platelet activation increased above a shear rate of 7200/s. Both VWF-FITC binding to platelets and VWF-self-association were shear stress-dependent processes. *P < .05 with respect to all other treatments at the given shear rate. ‡P < .05 with respect to 2300/s. †P < .05 with respect to pVWF-FITC alone at the same shear rate.
