Proactivator and activator levels of plasminogen in plasma as measured by caseinolysis.

A procedure is presented for the caseinolytic assay of plasminogen proactivator and activator levels in blood. The validity of the method was established and normal plasma proactivator levels were determined in 10 subjects. No detectible activator activity was found in these subjects. Venous occulsion produced a small rise in activator activity. Hageman-deficient and Fitzgerald trait plasmas did not produce activator activity after exposure to kaolin. The generation of activator activity in the Fitzgerald plasma was partly restored by the addition of purified high molecular weight kininogen, but the Hageman-deficient plasma was not corrected. The caseinolytic assay avoids some of the drawbacks which are inherent in methods which depend on fibrin dissolution for the detection of enhanced fibrinolytic states, provides a reproducible baseline, and may be sufficiently sensitive to detect changes of clinical interest.