Summary
A method for the assay of inhibitor of plasminogen activation in human serum, by means
of a standard clot lysis system, is described.
1. A pure, stable inhibitor of activation, E. A. C. A., was used in the preparation
of reference inhibitor curves.
2. The inhibitory activity of a serum specimen on plasminogen activation was expressed
quantitatively in units arbitrarily equated with the millimolarity of an E. A. C.
A. solution exerting an identical inhibitory effect.
3. The effects of time and temperature of storage of serum specimens, and of different
methods of preparation of serum, on the results of the test have been determined.
The use of different quantities of thrombin to clot the system did not alter the results.
4. No significant correlation was found between blood levels of inhibitor of plasminogen
activation and antiplasmin in a group of 66 normal individuals. The temperature stability
of the two types of inhibitor differed considerably, and the test system was significantly
inhibited by the known activation inhibitor E. A. C. A. in concentrations too small
to produce inhibition of a standard plasmin preparation. It was concluded that a discrete
inhibitor of plasminogen activation was measured by this method.
5. The mean level of inhibitor of activation in a group of 66 normal subjects was
2.5 u (S. D. =0.5 u). There were no significant age or sex differences, and alimentary
lipaemia was not found to cause significant changes.
