Table 1.
The EC50 for inhibition of the mean velocity index for thrombin generation by heparin in pooled normal human plasma
| Heparin | 0.2 pM TF EC50 (µM ± SEM) |
4 pM TF EC50 (µM ± SEM) |
Fold-increase |
|---|---|---|---|
| LMWH | 0.20 ± 0.02 | 0.57 ± 0.08 | 2.9 |
| ssLMWH | 0.27 ± 0.03 | 1.4 ± 0.14 | 5.1 |
| UFH | 0.012 ± 0.002 | 0.010 ± 0.001 | 1 |
| Fondaparinux | 0.13 ± 0.003 | 0.12 ± 0.006 | 0.9 |
Thrombin generation was initiated with 0.2 or 4 pM human tissue factor, 8.3 µM PC:PS vesicles, and 40 µg/ml CTI (plasma concentrations) in pooled normal human plasma in the presence of increasing heparin concentrations (LMWH and Fondaparinux 0–10 µM, UFH 0–1 µM). Duplicate wells were averaged to determine individual thrombin generation curves. The relative velocity index was plotted versus heparin concentration for each curve, and the EC50 value determined as described in Material and Methods. The mean EC50 ± S.E. was determined from 3 independent replicates (n=3). Fold-increase describes the ratio between EC50 values obtained in the presence of excess versus limiting TF concentrations.