FIGURE 9.

Zn²⁺ does not inhibit APC anticoagulant activity. APC (200 nm) was incubated in the presence of varying concentrations of Zn²⁺ (0–100 μm) for 20 min, and then 2 nm of APC from the reaction mixture was added to HUVEC monolayers incubated with FVa (1 nm) for 5 min. APC was allowed to inactivate FVa for 30 min, and the remaining Va activity was measured by adding FXa (5 nm) and prothrombin (1.4 μm) and measuring the amount of thrombin generated in a chromogenic assay. The rate of thrombin generation measured in the absence of APC and Zn²⁺ was taken as 100%. The data are presented as the means ± S.E. of five or six independent experiments. Conc, concentration.