Urokinase Inhibitor in Human Plasma

Abstract

For the demonstration of urokinase inhibition, an assay system was used consisting of porcine plasmin-ogen activated by human urokinase. After a certain period, activation was stopped by e-amino caproic acid, and plasmin activity measured with casein as substrate. A measure of urokinase inhibitor in plasma was obtained from the difference between the inhibition produced by adding plasma before activation and the inhibition produced by adding plasma after activation. It was demonstrated that normal, human plasma contains urokinase inhibitor. The inhibiting activity was the same in citrate plasma and serum. Inhibiting activity was present also when plasma was not allowed to get in contact with glass. Also the ester hydrolysing activity of urokinase was inhibited by normal, human serum. As substrate was used the synthetic amino acid ester α-N-acetyl-L-lysine methyl ester (ALME).

Key Words:

• Fibrinolysis
• plasmin inhibitor
• plasminogen activation
• urokinase inhibitor