Figure 1.

Different agonist concentrations can produce various percentages of coated platelets that have increased fibrinogen retention and decreased PAC-1 binding. (A) Correlation of coated-platelet percentage, determined by flow cytometry, with the degree of platelet stimulation. Platelets (100,000/μl) were stimulated with 10, 50, or 100 nM thrombin, 50 nM thrombin plus 0.1, 0.5, 1, or 3 ng/ml convulxin, and 100 nM thrombin plus 1, 5, 10, 100, or 1000 ng/ml convulxin (numbers 1–12 on the x axis, consistently). Typical data obtained from the experiments with platelets from three different donors are presented. (B and C) Dot plots for binding of PAC-1 (B) or anti-fibrinogen antibody (C) versus annexin V for platelets (100,000/μl) either unstimulated (left) or stimulated with 100 nM thrombin (right). The boxed area indicates the coated-platelet subpopulation. A typical experiment out of three performed with platelets from different donors is shown.