Influence of platelet count on thrombin-induced procoagulant activity.

(A) Gel-filtered platelets at different concentrations were activated with 0.05 to 2 U/mL thrombin; ● indicates100 000 platelets/μL; ○, 50 000 platelets/μL; ▪, 25 000 platelets/μL; ■, 12 500 platelets/μL; ▴, 5000 platelets/μL; ▵, 1000 platelets/μL (n = 3). (B) Annexin V-FITC-binding sites were determined on thrombin activated (1 U/mL) shaken (white column) and unshaken (black column) gel-filtered platelets (n = 6). The fluorescence of 5000 platelets per measuring point was determined by flow cytometry. Data are the mean of the indicated number (n) of experiments using platelets from different donors.