COORDINATED REGULATION OF TISSUE-TYPE PLASMINOGEN-ACTIVATOR AND PLASMINOGEN-ACTIVATOR INHIBITOR TYPE-1 GENE-EXPRESSION IN HYPOPHYSECTOMIZEDRAT OVARIES DURING GNRHA-INDUCED OVULATION

In this study we have demonstrated that both granulosa and theca-inter stitial cells of hypophysectomized rat ovaries are capable of synthesi zing tPA and PAI-1. Injection of a GnRH agonist can markedly induce th ese gene expressions in the ovary in a cell-specific and time-coordina ted manner, so that a surge of tPA mRNA and its activity in both granu losa and theca-interstitial cells was obtained just prior to ovulation . Theca-interstitial cells make PAI-1 become the most active in the ov ary. Both the amount PAI-1 mRNA and its activity in the cells reach th e maximum level 6 h before the tPA peak. By contrast, granulosa cells produce only a little amount of PAI-1 (most increase tPA activity), an d both PAI-1 mRNA and activity in the cells reach the maximum after ov ulation. The coordinated regulation of tPA and PAI-1 in the ovary may fine-tune the peak of tPA activity which may be important for the regu lation of the ovulatory process. The changes of tPA and PAI-1 in the o varian cells of hypophysectomized rats during GnRHa-induced ovulation are similar to that in intact rats during hCG-induced ovulation, sugge sting that the ovulatory process can be modulated by different regulat ory signals mediated by influencing the coordinated expression of both tPA and PAI-1.