Effect of botrocetin on shear-induced platelet aggregation in the presence of type 2M rvWFs.

Mock-transfected cell medium, rvWF-WT, or type 2M rvWF (-I662F, -E596K, -G561A, -R611H) were preincubated without (open bars) or with (solids bars) 1 μg/mL botrocetin. The mixture was added to washed platelets (0.5 × 10⁸/mL) in the shearing device and exposed to 4000 seconds^-1 for 5 minutes. The single platelet region was determined in the absence of shear and in the presence of mock-transfected cell medium and used as the reference for calculation of disappearance of single platelets (DSP). At 4000 seconds^-1, botrocetin was a potent inducer of SIPA in rvWF-WT. Type 2M rvWF-I662F, -E596K, and -G561A were increased to a similar extent as WT. In contrast, SIPA in rvWF-R611H reached 40%, in agreement with decreased botrocetin-induced binding to GPIb.