Effect of intracellular Ca²⁺ chelator dimethyl BAPTA, anti-GP Ib, or anti–GP IIb-IIIa on [Ca²⁺]i changes in the platelet adhesive and cohesive process on a vWF-coated surface under a shear rate of 1,500 s⁻¹. Experimental conditions were identical to those described in the Fig 2 legend, except that platelets were preincubated with 15 μmol/L of dimethyl BAPTA AM, 0.1 μmol/L of F(ab′)₂ of AP1 (anti-GP Ib), 1 μmol/L of c7E3 (anti–GP IIb-IIIa) for 30 minutes at 37°C before perfusion. Superimposed images (total 30 frames of 3 seconds) were obtained at 8 minutes of perfusion. Unlike the control without blockers, platelets preincubated with dimethyl BAPTA evidenced no [Ca²⁺]i elevation or no platelet cohesion. However, most platelets firmly adhered to the vWF surface to an extent comparable to that in the control experiment. Note the highly impaired firm adhesion (and no [Ca²⁺]i elevation or cohesion) in the presence of anti–GP IIb-IIIa antibody. In the presence of inhibitory anti-GP Ib, no significant platelet-surface interaction was observed at this shear rate.