Changes of ovarian plasminogen activator and inhibitor during gonadotropin-induced ovulation in rhesus monkeys

Changes of plasminogen activator (PA) and its inhibitor (PAI-1) activity and antigen have been investigated during PMSG/hCG induced ovulation in rhesus monkeys. It has been demonstrated that the ovarian tissue type PA (tPA) activity, which reaches maximum prior to ovulation and declines thereafter, is closely related to follicular rupture; significant increases in urokinase type PA (uPA) only occurs in granulosa cells after ovulation. Since the secretory activity of ovarian PAI-1 reaches its peak level 12-24 h earlier than tPA the rapid decrease in PAI-1 activity in the approach of ovulation is correlated with the elevation of tPA activity. It is, therefore, suggested that a counterbalance of tPA and PAI-1 activity within the ovary may play an important role in the ovulation mechanism, whereas uPA may be involved in the regulation of corpus luteum formation.