Gel Filtration of Fibrinolytic Components of Blood Plasma in Man and Rabbit.

This paper deals with a comparative aspect of the fibrinolytic system in man and rabbit, particularly relating to the "proactivator-like component" in rabbit plasma whose behavior is similar to proactivator A of human plasma fractionated by gel filtration and apparently acts as proactivator in the presence of a small amount of human globulin. The entity of this component has been remained yet quite obscure, but for the convenience it is tentatively called "proactivator-like component." As reported in the previous paper1) by the authors, two kinds of proactivators in human plasma, proactivator A and proactivator B, were respectively demonstrated by gel filtration using Sephadex G-200. These proactivators are easily converted into plasminogen activator by reacting with a relatively small amount of streptokinase (SK). As to rabbit plasma, it is well known that the fibrinolytic system does not respond to a small amount of SK2). This may imply that rabbit plasma practically contains no proactivator in a strict sense. However, great increase of the sensibility of rabbit plasma to SK with the addition of a very small amount of human plasma globulin is also known. The mechanism of the increasing sensibility of rabbit plasma to SK in the presence of human globulin has been generally explained as follows. Proactivator in the human globulin was activated by SK, then activator thus produced converted plasminogen of rabbit plasma to an active plasmin, even though direct evidence supporting the above mentioned hypothesis has not been established. In the present investigation, fractionation of rabbit plasma was conducted by gel filtration using Sephadex G-200. Then each fraction obtained was mixed with the solutions containing a very small amount of human plasma globulin and an adequate amount of SK. Then activator activity of each aliquot was assayed