Summary
In the in vitro generation of intermediate product I, in which non-purified components
are used, both prothrombin and foreign surface “contact” are essential for the formation
of optimum activity.
Most of the time interval required before optimum intermediate product I activity
is reached is the time needed for potentiation of intermediate product I as well as
for the conversion of prothrombin to thrombin.
In the system studied, it is felt that, in the absence of prothrombin, intermediate
product I activity is blocked by the presence of an inhibitor. The action of thrombin
would then be to overcome the inhibitor.
The apparent increase in factor IX activity, observed during the generation of intermediate
product I as measured by the one-stage method, is due to the non-specific clot-promoting
effect of intermediate product I on the assay.
