Effect of blocking GPIb-thrombin binding on thrombin-induced platelet procoagulant activity.
(A) Gel-filtered platelets were incubated with MoAb SZ2 (20 μg/mL) or glycocalicin (0.4 μmol/L) or Fragmin (40 IU/mL) and activated with thrombin (0.05-2 U/mL); ● indicates 25 000 platelets/μL; ▴, 25 000 platelets/μL in the presence of MoAb SZ2; ■, 25 000 platelets/μL in the presence of glycocalicin; ▵, 25 000 platelets/μL in the presence of Fragmin. The fluorescence of 5000 platelets per measuring point was determined by flow cytometry. (B) Thrombin generation by the prothrombinase complex on resting and thrombin-activated (0.5 U/mL) gel-filtered platelets and thrombin-activated (0.5 U/mL) gel-filtered platelets after pretreatment with 20 μmol/L SZ2 in the presence of 0.4 U/mL factor Xa and 6 μmol/L CaCl2; ○ indicates 25 000 platelets/μL; ●, 25 000 platelets/μL activated with thrombin; ▴, 25 000 platelets/μL, pretreated with SZ2, activated with thrombin. Data are the mean of 3 experiments using platelets from different donors.
