Platelets increase the cleavage of large VWF multimers under fluid shear stress. Reactions containing VWF (30 μg/mL) were performed as indicated with (+) or without (−) ADAMTS13 (2.5 U/mL), platelets (2 × 10⁶/μL), and fluid shear stress (16 dyne/cm², 10 minutes). The distribution of VWF multimers was assessed by 1.5% SDS-agarose gel electrophoresis.