Considerable data have shown that plasminogen activator (PA) may play an important role in the mechanism of ovulation. A recent report argued that PA is not a primary proteoIytic enzyme for follicular rupture because a dose of indomethacin that blocked ovulation did not inhibit ovarian PA content. To further clarify the specific role of PA in the ovulation, we have carefully examined the effect of indomethacin on the secretion of PA in granulosa and theca-interstitial (TI) cells following hCG or GnRH agonist administration in PMSG-primed hypophysectomized immature rats. We have also studies in vitro action of this compound on PA secretion in granulosa cells. The results indicate that indomethacin can only suppress hCG- and GnRH agonist-induced PA secretion, but not suppress the ovarian content of these enzymes. Considered data has shown that plasminogen activator (PA) may play an important role in the mechanism of ovulation. A recent report argued that PA is not a primary proteoIytic enzyme for follicular rupture because of a dose of indomethacin that blocked ovulation did not inhibit ovarian PA content To further clarify the specific role of PA in the ovulation, we have carefully examined the effect of indomethacin on the secretion of PA in granulosa and theca-interstitial (TI) cells following hCG or GnRH agonist administration in PMSG-primed hypophysectomized immature rats. We have also studies in vitro action of this compound on PA secretion in granulosa cells. The results that that indomethacin can only suppress hCG- and GnRH agonist-induced PA secretion, but not suppress the ovarian content of these enzymes.