Proteinases and proteinase inhibitors in uterine fluid with special reference to IUD-users.

Abstract

This is a thorough review of the literature of findings from studies dealing with fibrinolytic activity of human uterine fluid during the menstrual cycle. The activation of plasminogen to plasmin was found to control fibrinolytic activity. Urokinase and tissue activator 2 types of plasminogen activators were found to be responsible for the activation of plasminogen. Fibrinolytic activity varied throughout the menstrual cycle increasing during the proliferative phase to a maximum at midcycle declining to low values at the luteal phase and increasing again in the premenstrual phase. The combined action of a high activator and low inhibitor concentration at midcycle resulted in high fibrinolytic activity and vice versa in the luteal phase. IUD users and nonusers exhibited the same cyclic variation in the fibrinolytic activity of uterine fluid. The activity however was lower in IUD users. The difference in activity between the 2 groups of women was presumed to be due to inhibition or inactivation of urokinase. IUDs may exert their contraceptive effect in part through a disturbance in the balance between proteinases and their inhibitors in the uterine fluid thereby disturbing the intrauterine stages of reproduction. These disturbances may be responsible for some of the side effects experienced with IUDs.