Distinction of Plasma Inhibitor of Activator-Induced Clot Lysis from Antiplasmins

A fraction of human plasma prolongs the activator-induced clot lysis time and inhibits plasminogen activation by the plasminogen activators derived from various sources (urine and tissues). This fraction, designated as antiactivator fraction, was separatid from antiplasmin fractions (α₂-macroglobulin and α₁-antitrypsin) by gel filtration and affinity chromatography on Sepharose coupled with IgG of antiserum to α₁-antitrypsin. Anti-activator fraction thus obtained exerted little antiplasmin activity but inhibited strongly activator-induced clot lysis.

Inhibitory effect of plasma on urokinase-induced clot lysis (antiactivator activity) was assayed in various diseases and compared with antiplasmin activity. No correlation was found between the two activities, and it was concluded that the two activities are independent and are ascribed to two different entities.