Steroids and follicular rupture at ovulation

Area of Science:

• Reproductive Endocrinology
• Molecular Biology
• Cellular Physiology

Background:

• Ovulation involves complex hormonal regulation, including gonadotropin surges and ovarian steroidogenesis.
• Ovarian follicular rupture is a critical event in ovulation, requiring precise molecular mechanisms.
• Plasminogen activators (PAs) have been implicated in the degradation of the follicular wall during ovulation.

Purpose of the Study:

• To review the role of ovarian steroidogenesis in follicular rupture at ovulation.
• To investigate the relationship between steroidogenesis, gonadotropin stimulation, and plasminogen activator activity.
• To elucidate the specific contribution of follicular steroids to ovulation.

Main Methods:

• Review of existing studies on steroidogenesis inhibitors and ovulation.
• In vivo experiments using gonadotropins and ovulation triggers (e.g., hCG).
• Assessment of plasminogen activator (PA) activity and synthesis in response to steroidogenesis modulation and hormonal stimulation.

Main Results:

• Inhibitors of steroidogenesis blocked follicular rupture, and RU 38486 partially inhibited hCG-induced ovulation.
• LH stimulation of PA activity was partially blocked by steroidogenesis inhibitors but restored by progesterone, testosterone, and estradiol-17 beta.
• Gonadotropin stimulation selectively increased tissue-type PA (t-PA) synthesis, not urokinase-type PA (uPA).
• Inhibition of steroidogenesis reduced t-PA synthesis, which was reversed by estradiol-17 beta addition.

Conclusions:

• Follicular steroidogenesis is a necessary component for successful ovulation.
• Follicular steroids, likely estrogen, play a key role in the preovulatory surge of follicular t-PA activity.
• The interplay between gonadotropins, ovarian steroids, and PA system is vital for ovulation.