Effect of different inhibitors on the dynamic parameters of single platelets interacting with immobilized VWF. Platelets loaded with FLUO 3–AM were suspended at a count of 1 × 107/mL with homologous washed red cells in Hepes-Tyrode buffer containing 10 μg/mL human VWF, 500 μg/mL human fibrinogen, 2 mM Ca⁺⁺, and 2 mM Mg⁺⁺. The suspension was perfused over immobilized VWF at the shear rate of 3000 s^–1 for 90 seconds, after which all the surface interacting platelets were monitored in real time for the next 30 seconds during translocation to measure their average velocity (A) or arrest time (B). Apyrase was used at the final concentration of 5 ATPase U/mL; the PI 3-K inhibitor LY294002, at 25μM; the PLC inhibitor U73122, at 20 μM; PGE₁ at 10 μM; and all the other inhibitors as described in the legend to Figure 1. The results represent the mean plus or minus the 95% confidence intervals of the values measured for 180 to 250 platelets in 4 separate experiments. The symbols indicate values that are significantly different from the corresponding controls (*P < .01; ¶P < .05; Student t test).