Coated platelets are formed following dual agonist stimulation. C57BL/6 platelets were stimulated with the indicated agonists for 7 minutes and the surface retention of (A) fibrinogen, (B) VWF, or (C) binding of PE-JON/A was measured by flow cytometry. Dashed lines indicate unstimulated platelets; solid lines, agonist-activated platelets. Regions M1 and M2 correspond to populations of activated and coated platelets, respectively. The mean fluorescence for FITC-antifibrinogen (Fbg) on each population in panel A was unstimulated, 9; activated (M1), 80; coated (M2), 718.