Postovulatory decrease in estrogen production is caused by the diminished supply of aromatizable androgen to ovarian...

Area of Science:

• Reproductive endocrinology
• Steroidogenesis
• Hormonal regulation of ovulation

Background:

• Ovulation is triggered by gonadotropins like PMSG and hCG.
• Estradiol-17 beta levels decrease significantly after ovulation.
• Ovarian enzymes 17 alpha-hydroxylase and C17-C20 lyase activity is affected by gonadotropin treatment.

Purpose of the Study:

• To investigate the effect of testosterone administration on ovarian estradiol-17 beta content in immature rats post-ovulation.
• To elucidate the role of ovarian androgen supply in regulating estradiol production after PMSG/hCG-induced ovulation.

Main Methods:

• Immature female rats were treated with PMSG and hCG to induce ovulation.
• Testosterone was administered to ovulated rats.
• Ovarian content of estradiol-17 beta was measured.
• Previous findings on ovarian enzyme activity (17 alpha-hydroxylase and C17-C20 lyase) were considered.

Main Results:

• Testosterone administration led to a significant increase in ovarian estradiol-17 beta content.
• This increase occurred despite a previously observed decrease in ovarian 17 alpha-hydroxylase and C17-C20 lyase activity post-PMSG/hCG treatment.

Conclusions:

• The post-ovulatory decrease in serum estradiol-17 beta is attributed to a limited supply of aromatizable androgens to ovarian aromatase.
• Diminished activity of ovarian 17 alpha-hydroxylase and C17-C20 lyase is the likely cause of this androgen shortage.
• Testosterone administration can overcome this limitation, supporting the role of androgen precursors in estradiol synthesis.