Effect of IUD on urokinase-like immunoreactivity and plasminogen activators in human uterine fluid.

The coexistence of two types of plasminogen activators in human uterine fluid was demonstrated. Immunologically, one was urokinase-like and the other tissue activator-like. Both activators contributed to the fibrinolytic activity of uterine fluid. Urokinase-like immunoreactivity decreased from the proliferative phase to the luteal phase and increased premenstrually. The increase in fibrinolytic activity premenstrually was ascribed mainly to an increase in concentration of the urokinase-like plasminogen activator. A much higher urokinase-like immunoreactivity was found in the uterine fluid from IUD-users than from non-users. The fibrinolytic activity of the uterine fluid, which in contrast to that of the endometrium is known to be depressed in IUD-users, was inhibited by an antiserum against the tissue activator but only weakly influenced by an antiserum against urokinase. This indicates the presence of urokinase inhibitors in the uterine fluid of IUD-users with a capacity to inhibit the enzymatic activity of the urokinase-like plasminogen activator.