Inhibition of the frequency of [Ca⁺⁺]_ielevations in platelets interacting with immobilized VWF under flow. A blood cell suspension, prepared as described in the legend to Figure 2, was perfused over immobilized VWF at the shear rate of 3000 s^–1. After an initial 90-second perfusion, all platelets interacting with the surface in a 30-second period were identified and analyzed in the absence or presence of different inhibitors, used as described in the legends to Figure 1 and Figure 2. The number of platelets exhibiting at least one [Ca⁺⁺]_i elevation (activated platelets) was measured, and the percentage of platelets showing α/β (A) or γ (B) peaks relative to the total number of surface interacting platelets was calculated. The bar graph in panel C shows the number of α/β peaks in each single activated platelet treated with the anti-α_IIbβ₃ antibody, LJ-CP8 (100 μg/mL), to block γ peaks. The results represent the mean plus or minus the 95% confidence intervals of the values measured in 4 different experiments. The symbols indicate values that are significantly different from the corresponding controls (*P < .01; ¶ P < .05; Student t test).