Summary
Normal human plasma contains acid-stable as well as labile plasminogen activators.
The activity of activators in plasma euglobulins was inhibited by EACA in an uniform
pattern, similar to that obtained with the major activators in human uterine tissue
or with the purified porcine tissue activator, but different from the patterns obtained
with plasmin or with urokinase.
Gel filtration at high ionic strength separated activators corresponding to particle
sizes of 60,000 dalton and about 10,000 dalton, corresponding to two activators similarly
obtained from human tissue. The 60,000 dalton activator was precipitated in the euglobulin
fraction. Its concentration increased in plasma after exercise. The 10,000 dalton
activator was found mainly in the supernatant. Gel filtration in 0.15 M solutions
yielded activators in fractions of molecular sizes of 100-140,000 dalton and 200,000
dalton or larger.
The activity of normal and exercise euglobulins was inhibited by antiserum to a plasminogen
activator prepared from porcine tissue, but it was not inhibited by antiserum to urokinase.
Plasminogen activators in human plasma euglobulins resembled immunochemi- cally the
activators in human uterine tissue.
