Tissue factor–independent thrombin generation is associated with release of a soluble fragment of GPV from the platelet surface.

Washed normal platelets and red cells (200 000 platelets/μL; hematocrit 40%) were perfused over collagen type III for 5 minutes at 1600 s⁻¹ in presence of an RGD-containing peptide (dRGDW; 200 μM) in the absence or presence of the thrombin-generating system (1.2 μg/mL rFVIIa, 10 μg factor X, 20 ng/mL prothrombin, 3 mM CaCl₂). The perfusate was collected in EDTA (1:10, vol/vol), cells were removed by centrifugation, and soluble GPV was measured in the supernatant. Shown is the mean of 4 independent experiments performed in duplicate. Error bars indicate SEM.