Thromb Haemost 1998; 80(04): 578-584
DOI: 10.1055/s-0037-1615424
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Active Site-inactivated Factors VIIa, Xa, and IXa Inhibit Individual Steps in a Cell-based Model of Tissue Factor-initiated Coagulation

Marianne Kjalke
1   From the Center for Thrombosis and Hemostasis, University of North Carolina at Chapel Hill, NC
3   From the TF/FVIIa Research, Novo Nordisk, Maaloev, Denmark
,
Dougald M. Monroe
1   From the Center for Thrombosis and Hemostasis, University of North Carolina at Chapel Hill, NC
,
Maureane Hoffman
2   From the Department of Pathology, Duke University, Durham, NC, USA
,
Julie A. Oliver
1   From the Center for Thrombosis and Hemostasis, University of North Carolina at Chapel Hill, NC
2   From the Department of Pathology, Duke University, Durham, NC, USA
,
Mirella Ezban
3   From the TF/FVIIa Research, Novo Nordisk, Maaloev, Denmark
,
Harold R. Roberts
1   From the Center for Thrombosis and Hemostasis, University of North Carolina at Chapel Hill, NC
› Author Affiliations

Supported in part by grants R01 HL48320 and T32 HL07149 from the National Institutes of Health
Further Information

Publication History

Received 09 December 1997

Accepted after revision 29 June 1998

Publication Date:
08 December 2017 (online)

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Summary

Factors VIIa, Xa, and IXa play different roles in the initiation of tissue factor-dependent coagulation. The consequences of competing with the different enzymes were investigated, thereby examining the effects of inhibiting the initiation process at different steps. Active site-inactivated factors VIIa, Xa, and IXa (FVIIai, FXai, and FIXai, respectively) were added to various cell-based assays mimicking the individual steps in tissue factor-initiated coagulation. In an assay involving tissue factor-expressing monocytes, coagulation proteins and unactivated platelets, FVIIai and FXai inhibited platelet activation and thrombin generation while FIXai only inhibited thrombin generation. FVIIai inhibited factor Xa generation and subsequent thrombin generation on monocytes, while FXai inhibited thrombin generation on the monocytes as well as on the activated platelets. FIXai had no effect on factor Xa or thrombin generation on the monocytes, but inhibited factor Xa and subsequent thrombin generation on the activated platelets. FVIIai had no effect on the reactions taking place on the activated platelets. The data confirm a model where tissue factor/factor VIIa mediates factor Xa generation and subsequent prothrombin activation on the tissue factor-bearing cells. Thrombin then activates platelets, which serve as the physiologically important surface for large-scale thrombin generation.