The Inhibition of Tissue Plasminogen Activator and Urokinase-Induced Fibrinolysis by Some Natural Proteinase Inhibitors and by Plasma and Serum from Normal and Pregnant Subjects

Abstract

A number of natural proteinase inhibitors produced only small differences in the inhibition of fibrinolysis caused by porcine ovary tissue plasminogen activator or by human urokinase, despite the existence of large differences in inhibition in the presence of aminocaproic acid (or related compounds). A labile inhibitor present in fresh serum inhibited tissue activator-induced fibrinolysis more than urokinase-induced fibrinolysis. Plasma or serum from late pregnancy showed a selective increase in the inhibition of urokinase-induced fibrinolysis demonstrable at medium and low concentrations of activator.