Quantitative Determination of Activity of Streptococcal Fibrinolysin

Abstract

A survey of the literature indicates that very few quantitative studies have been made on streptococcal fibrinolysin. The majority of attempts which have been made have involved serial dilutions of cultures or culture-filtrates which were incorporated in fibrin clots and in this way tested for lytic activity. Van Deventer 1 proposed as a unit of fibrinolysin that amount causing dissolution of a plasma fibrin clot at the end of 24 hours. Fraser and Madison 2 used essentially the same technic with the substitution of fibrin prepared from freshly-prepared fibrinogen and thrombin solutions. Later, Madison and Taranik 3 attempted a still further standardization of the test. In this procedure, the highest dilution causing lysis at the end of 2 hours contained one unit of fibrinolytic activity.

Massell, Mote and Jones 4 in an extensive study of antifibrinolysins devised a method for measuring the amount of antifibrinolysin present in a serum, based on their belief that fibrinolysin is quantitatively neutralized by antifibrinolysin. By appropriate modification of their procedure, it is possible to compare the lytic activity of 2 or more lysins, but absolute quantitative results are not obtained.

Lack of uniformity in the fibrin used as substrate, the effects of various media components, and the effects of other enzymes in the culture filtrates have seemed to render difficult the development of a satisfactory quantitative test. Further, in none of these reports has any data on retests been given, so it is impossible to evalute the reliability of the various procedures from the standpoint of reproducibility. Also, it has been noted in this laboratory that freshly-prepared fibrinogen samples vary in their susceptibility to lysis. It is believed that the chief factor in these differences in susceptibility is the variable protein content of such fibrinogen solutions.

With a standardized, stable substrate available through the use of dried fibrinogen and dried prothrombin, 5 , 6 the possibility of the construction of a satisfactory quantitative fibrinolysin test was investigated.