Fibrin-Agar-Plate Method, a New Method for Estimation of Fibrinolytic Activity.

Abstract

The fibrin plate method by Astrup and Mullertz (1952) is a typical one among the methods for measuring fibrinolytic activities.
A new method of the authors in which agar gel was used as a support in fibrin plate was named “Fibrin-Agar-Plate (F.A.P.)” method.
The principle of the F.A.P. method is the same as that of the fibrin plate method and the procedures are similar to those in radial immunodiffusion method.
F.A.P. was prepared in Petri dishes (9 cm in diameter) in a following way: Seven ml of a 2 per cent agar solution (Difco) was mixed with 3 ml of an aqueous solution containing 8 mg of fibrinogen at 40 to 50°C (final concentration of agar was 1.4% and that of fibrinogen 0.08%, pH. 7.8). When the agar-fibrinogen mixture has solidified at room temperature, 1.5 ml (5 units) of thrombin solution was added. Afilter paper (8.6 cm diameter) was placed on it so that the surface of the agar plate became uniformly wet. It was allowed to stand at 4°C for not less than 5 hours. Then the filter paper was taken off and the holes with a diameter of 2 mm were punched out, samples (2 μl) poured in and the plates were kept at 37°C for 18 hours. The size of the zone of lysis was taken as a measure of fibrinolytic activity.
Unlike fibrin plate method, the F.A.P. method requires neither a wide horizontal laboratory desk nor skill. The zones of lysis produced show a sharp contrast with the fibrin substrate and were almost always circular.
The F.A.P. method is reproducible and a close correlation with fibrin plate method has been obtained.