FIGURE 5.

Inhibition of activated protein C amidolytic activity by zinc ions. A, APC (circles) or GD- APC (squares) (10 nm) were incubated for 5 min with varying concentrations of zinc ions (0–200 μm) in the absence (filled symbols) or presence (open symbols) of the physiological concentration of Ca²⁺ (1.1 mm). The amidolytic activity of APC was then determined using chromogenic substrate S-2366. B, APC (○) or GD-APC (□) (10 nm) was incubated with 100 μm ZnCl₂ in the presence of varying concentrations of CaCl₂ for 10 min, and the amidolytic activity of APC was then determined using S-2366. The amidolytic activity of APC measured in the absence of Ca²⁺ and Zn²⁺ was taken as 100%. The effect of varying concentrations of Ca²⁺ with no Zn²⁺ on APC (●) and GD-APC (■) amidolytic activity was also measured. Conc., concentration.