Effect of fondaparinux or heparin on clotting induced by RecombiPlasTin or coagulation enzymes. After incubating 1/1500-diluted RecombiPlasTin, 0.13nM fXa, 5nM fIXa, 0.5nM fXIa, or 20nM fXIIa in plasma containing fondaparinux (closed circles) or heparin (open circles), at the indicated concentrations, for 10 minutes at 37°C, clotting was initiated by addition of CaCl2 to 20mM. For thrombin-initiated reactions, CaCl2 was omitted to avoid feedback activation of coagulation, and thrombin (fIIa) was added to 5nM after the 10-minute incubation at 37°C. Absorbance was monitored up to a maximum of 14 000 seconds, and time to clot was determined. The symbols represent the mean of ≥ 3 separate experiments, and the lines above and below the symbols reflect the SD. The arrows represent the contact, tissue factor, and common pathways of coagulation.
