Summary
A urokinase-activated plasmin (UK-plasmin) preparation was assayed against the International
Reference Preparation for Plasmin (IRP-plasmin) using caseinolytic, fibrinolytic,
fibrinogenolytic and chromogenic assay methods. The relative potency (using multi-dose
bioassays) was estimated by the fibrinolytic method to be about twice that obtained
by the caseinolytic, fibrinolytic and chromogenic assay methods. It was found that
the UK-plasmin binds to fibrin to a greater extent than does the IRP-plasmin and this
is advanced as an explanation for the discrepancy between assay methods. This difference
in the binding of the two plasmins to fibrin may mean that it will be difficult to
compare the fibrinolytic activities of various plasmin preparations.
It is also shown that, during thermal degradation, the IRP-plasmin loses fibrinolytic
activity more rapidly than amidolytic activity.
Keywords
Plasmin - Standardisation - Chromogenic substrate - Clot lysis assay