Activation of coagulation factor X in human semen

Area of Science:

• Coagulation science
• Reproductive biology
• Biochemistry

Background:

• Tissue factor (TF) is crucial for initiating blood coagulation.
• TF is present in human semen, associated with prostasomes.
• The TF-fVIIa complex activates factors X and IX in coagulation.

Purpose of the Study:

• Investigate semen's capacity to activate factor X.
• Characterize the components and limitations of TF-mediated coagulation in semen.
• Explore variations in TF-fVII activity in infertile patients.

Main Methods:

• Assessed factor X activation in seminal plasma.
• Measured TF-fVII activity in semen specimens.
• Used calcium and ionophore A23187 to stimulate activity.
• Employed anti-TF antibody to block activation.

Main Results:

• Seminal plasma contains TF, primarily activating added factor X via TF-fVIIa.
• Semen lacks endogenous factor X but possesses fVII-like activity, limiting TF's potential.
• TF-fVII activity varied significantly in infertile patients; no correlation with abstinence, pH, sperm count, or motility.
• Calcium/ionophore treatment generated additional TF-dependent activity, suggesting a non-factor X substrate.

Conclusions:

• Semen's factor X activation is limited by fVII availability and lack of endogenous factor X.
• TF-fVII activity in semen shows high inter-individual variability.
• A novel TF-fVIIa substrate, possibly factor IX, exists in seminal plasma.