Prothrombinase activity generated by single and dual agonists.

Gel-filtered platelets were stimulated with various single- and dual-agonist combinations for 10 minutes as described in “Materials and methods.” Platelets were then added to exogenous Factor Xa and prothrombin, and the initial rate of prothrombin activation was determined. Panel A depicts a representative experiment and demonstrates that the initial rates of thrombin generation were linear for up to 4 minutes. Agonist concentrations were 5 nmol/L thrombin, 500 ng/mL convulxin, and 2 μmol/L A23187. Panel B represents the prothrombinase activity (nmol/L thrombin generated per minute) for various agonists. Ionophore (A) was 2 μmol/L; thrombin (T), 5 nmol/L; and convulxin (CVX) concentration was 500 ng/ml unless specifically designated (ng/mL) otherwise. Bars represent mean ± 1 SD; n = 3.