[Plasminogen activator activity in mouse ovaries during periovulatory period]

Immature mice were injected subcutaneously with 5 IU PMSG for 2 days to stimulate follicle development, which was followed by administration of 5 IU hCG to induce ovulation. The ovaries were removed at various periovulatory stages for preparing ovarian homogenates, granulosa cells and cumulus-oocyte complexes. The activity of plasminogen activator in the samples, separated by SDS-PAGE, were determined by fibrin-overlay technique. The results show that 15% of the gonadotropin-treated animals were ovulated 8h after hCG administration, about 6-8h earlier than that occurred in rat. Moreover, both tPA, and uPA activity were stimulated following PMSG treatment in ovarian homogenates and granulosa cells. Subsequent hCG injection further increased the two types of PA activity in a time-dependent manner, reaching maximum 4-8h after hCG treatment, and declined following ovulation. Greater uPA activity (70%) in the cultured mouse granulosa cells was found. It is, therefore, suggested that both tPA and uPA may be involved in the regulation of ovulation in mouse. The cumulus-oocyte complexes contained mainly tPA, which activity showed a time-dependent increase and reached a maximum between 12-24h after hCG treatment. Since cumulus-oocyte complexes collected from oviducts post ovulation still retain a considerable amount of tPA, the enzyme in the complexes may also play a role in the process of cumulus dispersion, oocyte transportation and implantation.