A new sensitive assay for bovine activated factor XI (factor XIa) using a reconstituted coagulation cascade system

Area of Science:

• Biochemistry
• Hematology
• Enzymology

Background:

• Activated Factor XI (Factor XIa) plays a crucial role in the intrinsic pathway of blood coagulation.
• Quantifying Factor XIa activity is essential for understanding hemostasis and thrombosis.
• Existing methods may have limitations in sensitivity or specificity for certain applications.

Purpose of the Study:

• To develop and validate a sensitive assay for quantifying bovine activated Factor XI (Factor XIa) in vitro.
• To assess the utility of the assay for kinetic analysis of surface-mediated Factor XI activation.

Main Methods:

• A novel assay was developed measuring amidolytic activity of thrombin generated from bovine Factors XIa, IX, X, prothrombin, and washed bovine platelets.
• The assay's sensitivity to varying Factor XIa concentrations was determined.
• Interference from other plasma components and surface-mediated activation factors was evaluated.

Main Results:

• The assay demonstrated a linear relationship between thrombin generation rate and Factor XIa concentration (in fmoles).
• The assay system showed minimal interference from plasma kallikrein, Factor XIIa, high-molecular-weight kininogen, amylose sulfate, or sulfatide.
• Freeze-thawed platelets were used to block further Factor XIa generation after surface activation.

Conclusions:

• A sensitive and specific in vitro assay for bovine Factor XIa has been successfully developed.
• This assay is suitable for kinetic analysis of surface-mediated activation of Factors XII and XI.
• The method is not applicable to Factor XI activation within plasma but provides a valuable tool for surface-based studies.