Effect of recombinant ADAMTS13 on platelet thrombus formation on fibrillar collagen type I under flow conditions. The bar graph shows the volume of thrombi formed after perfusion of whole blood containing 93 μM PPACK over a surface of 62 500 μm² coated with collagen type I fibrils. The blood was supplemented or not with recombinant ADAMTS13, as indicated, which was added at least 15 minutes before perfusion. The protease activity added corresponded to 17.5% of that present in normal blood. The wall shear rate was 1500 s^-1 for 7 minutes or 6000 s^-1 for 4.5 minutes, as indicated. The values represent the mean ± SEM of 2 experiments performed with blood from different donors. The results obtained with or without addition of ADAMTS13 were not significantly different.