Figure 4.

P2Y₁₂ Surface Expression and ADP Response

(A) Representative flow cytometry histograms of antibody staining for the P2Y₁₂ receptor on resting platelets isolated from neonatal cardiac patients (NCP) versus healthy adults. Histograms of antibody staining for the human GPIbα (CD42b) and integrin αIIbβ3 (CD61) are shown for comparison. (B) Mean fluorescence intensities (MFI) of P2Y₁₂. Results are presented in absolute arbitrary units. (C to F) Concentration response curves for the determination of EC₅₀ (concentration of a drug that gives half-maximal response) values for adenosine diphosphate (ADP) as measured by light transmission aggregometry using purified platelets from neonatal and pediatric patients with congenital heart disease or healthy adult volunteers in the presence of fibrinogen (mean ± SEM). Concentrations of agonist are plotted in log form, and all data were normalized to the maximal concentration of ADP (20 μM). Data represent the mean ± SEM. n = 12 (age 0 to 28 days); n = 7 (age 1 to 10 years); n = 7 (age 11 to 18 years); n = 12 for adults. Statistical significance determined by using the Mann-Whitney U test.