Figure 5. Inhibition of P2Y₁₂ receptors affects collagen-dependent thrombus formation at high but not low shear rate.

Citrate-anticoagulated human blood, recalcified with CaCl₂/MgCl₂ in the presence of 2 pM tissue factor, was perfused over Horm type I collagen at a shear rate of 300 or 1000 s⁻¹. Blood samples were preincubated with vehicle, ticagrelor (20 µM) or cangrelor (10 µM), as indicated. (A) Representative phase-contrast images after 4 min of perfusion (bar = 20 µm). (B) Average size of thrombi formed in treated blood samples at different shear rates. (C) Frequency distribution of feature size on coverslips; estimated numbers of platelets per feature (aggregate) were: 9–24 (white), 24–75 (light gray), 75–400 (dark gray) and >400 (black). (D) Number of disaggregation events from individual aggregates in the 4th minute of blood perfusion at 300 or1000 s⁻¹. Data are means ± SE (n = 3–9), *p<0.05 compared to vehicle.