Quantitative comparison of the effect of Rho-kinase inhibition and chelation of cytosolic Ca²⁺ on platelet shape change induced by various agonists. Shown are untreated controls (□), samples incubated with Y-27632 (20 μmol/L; ▪), and samples pretreated with BAPTA-AM (20 μmol/L) and EGTA (2 mmol/L; ▩). (a) Stimulation conditions that were not associated with an increase in cytosolic Ca²⁺ (see Fig 1): lower concentrations of thrombin (0.01 to 0.04 U/mL), YFLLRNP (300 μmol/L), U46619 (50 nmol/L). (b) Stimulation conditions that induced a significant increase in cytosolic Ca²⁺: higher concentrations of thrombin (0.05 to 0.2 U/mL), ADP (2 μmol/L), CRP (0.05 μg/mL), ionomycin (100 nmol/L). Values are mean ± SD of 4 to 6 independent experiments. Asterisk (*) indicates absence of shape change in all experiments.