Enzymatic activity of CyPA is responsible for defective Ca²⁺ mobilization. Defective agonist-induced Ca²⁺ mobilization and impaired SOCE in Cypa^+/+ platelets pretreated with 1 μg/mL of CsA. (A) Maximal increase in cytosolic Ca²⁺ concentration of Cypa^+/+ (black bars) and CsA-treated Cypa^+/+ platelets (gray bars) after stimulation with thrombin (0.02 U/mL) and CRP (10 μg/mL), respectively. Arithmetic means of maximal [Ca²⁺]_i ± SD (n ≥ 6 per group) before (left panel) and after (right panel) the addition of 1mM Ca²⁺. **P < .01; ***P < .001. (B) Representative time course of intracellular Ca²⁺ mobilization in Cypa^+/+ (black line) and CsA-treated Cypa^+/+ platelets (gray line) after exposure to 5μM thapsigargin for 10 minutes and subsequent addition of 1mM extracellular Ca²⁺. (C) Mean values of maximal Δ [Ca²⁺]_i ± SD (n ≥ 5 per group) before and after the addition of 1mM Ca²⁺. **P < .01; ***P < .001.