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Updated: May 15, 2026

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay
Published on: September 9, 2012
A new regulatory function of activated factor V: inhibition of the activation by tissue factor/factor VII(a) of
R Al Dieri1, S Bloemen, H Kelchtermans
1Synapse BV, CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands. r.aldieri@thrombin.com
Background:
We observed that minute amounts of thrombin or the enzyme Russell's viper venom activating factor V (RVV-V) added to plasma strongly diminish the potential of that plasma to generate thrombin after being triggered by tissue factor.
Objective:
To find the mechanism behind this phenomenon.
Methods And Results:
Thrombin generation (TG) initiated by tissue factor (TF) is strongly and dose-dependently inhibited by addition of activated factor V (FVa) or by addition of a factor V activator (thrombin or RVV-V). No inhibition is seen when TG is triggered via the intrinsic pathway or by direct activation of factor X. The effect is independent of proteins C and S and tissue factor pathway inhibitor (TFPI). In factor VII-deficient plasma the effect is seen when it is spiked with recombinant factor VII (FVII) and to a much lesser extent when spiked with recombinant FVIIa. In a purified system, FVa also dose-dependently inhibits the activation of FX by TF/FVII(a). The inhibitory effect is neutralized by antibodies against the light chain of FVa but not by antibodies against the heavy chain.
Conclusions:
Our observations can be explained by assuming that FVa, via its light chain, binds to the complex TF/FVII(a) and prevents it from activating FX. We assume that this mechanism reduces the possibility that thrombin and factor Xa escaping from a wound area into the circulation, together with blood-borne tissue factor, would trigger intravascular coagulation.
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