Platelet cytoplasmic Ca⁺⁺ response to various agonists measured using fura-2 fluorescence.

Several agonists such as ADP (10 μmol/L), TRAP (1 μmol/L), and thrombin (0.05 U/mL) caused a partial reduction in a second chemokine-induced signal or vice-versa. The ADP receptor inhibitor, AR-C66096 (100 nmol/L), also caused a partial but not complete inhibition of Ca⁺⁺ signaling by chemokines and the other agonists. The signals were lower but not cross-desensitized in the presence of apyrase (5 U/mL, not shown). The results shown are typical of at least 3 similar experiments.