GPIbα accelerates rFVIIa-mediated thrombin generation. Platelets were pretreated with OSE (160 μg/mL, ----, ○) or vehicle (—, ●) for 30 minutes at 37°C and subsequently stimulated with a combination of convulxin (100 ng/mL) and SFLLRN (100 μM). (A) Next, thrombin generation was followed in time after addition of 25 nM VIIa in the presence of plasma concentrations of coagulation factors VII, X, II, V, and Ca2+, and inhibitors TFPI and antithrombin III. Samples were taken at indicated time points, and the amount of thrombin generated was calculated. (B) Platelets were reconstituted in “artificial” hemophilic plasma (final concentration, 200 000/μL), and coagulation was started by the addition of 25 or 100 nM rFVIIa. The formation of thrombin was followed in time using a commercially available thrombin generation assay. (C) Quantification of the initial slope of plasma-based thrombin generation curves as shown in panel B. Shown are mean values from thrombin generation curves generated from 8 different donors in which thrombin generation curves were generated in “artificial” hemophilic plasma with 25 or 100 nM of rFVIIa in the absence or presence of OSE pretreatment. Error bars represent SD.
