Effect of urokinase antiserum on plasminogen activators: demonstration of immunologic dissimilarity between plasma plasminogen activator and urokinase.

Antiserum against purified human urokinase was produced by immunization of Hartley strain guinea pigs. The antiserum was capable of neutralizing the plasminogen activator activity of the antigen and of native urokinase in human urine. The antiserum did not inhibit plasminogen activators of bacterial origin, i.e., streptokinase and staphylokinase; neither did it inhibit urokinase from nonprimate mammals, i.e., dog, pig, rabbit, guinea pig, nor tissue activator or tissue culture supernatants from porcine sources. Partial cross-reactivity against urokinase from primates, i.e., rhesus monkey and baboon, was noted as well as with supernatant from rhesus kidney tissue culture. In vitro studies showed lack of immunologic identity between human urokinase and human milk activator or human tissue activator from adrenal sources but demonstrated immunologic identity between human urokinase and the supernatant from human kidney tissue culture. In vivo studies in man failed to show detectable levels of urokinase activity in peripheral venous or renal venous blood under a variety of clinical states and when stimuli such as exercise, electroshock therapy, or nicotinic acid were used to enhance plasminogen activator activity in the plasma. The results establish that human plasma activator, milk activator, and tissue activator from the adrenals are immunologically distinct from human urokinase.