Inhibin secretion by the sheep ovary

Area of Science:

• Reproductive Endocrinology
• Ovarian Physiology
• Hormone Assays

Background:

• Inhibin plays a crucial role in regulating reproductive functions.
• Understanding inhibin's secretion pathway is vital for reproductive health research.
• Existing methods for inhibin measurement have limitations.

Purpose of the Study:

• To validate an in-vitro bioassay for measuring inhibin activity in ovine plasma and lymph.
• To investigate the source and transport route of inhibin in ewes.
• To determine the half-life of inhibin in ovine plasma.

Main Methods:

• Validated an in-vitro bioassay using rat pituitary cells to measure FSH.
• Administered ovine follicular fluid to ovariectomized ewes and measured plasma inhibin.
• Collected ovarian lymph and peripheral/ovarian venous plasma from ewes.
• Induced folliculogenesis with PMSG and destroyed follicles via electrocautery.

Main Results:

• The bioassay successfully measured dose-dependent increases in inhibin activity.
• Inhibin was detected in ovarian lymph but not in peripheral or ovarian venous plasma.
• Follicle destruction led to a rapid decline in ovarian lymph inhibin secretion.
• Inhibin's plasma half-life was determined to be approximately 45-50 minutes.

Conclusions:

• Antral follicles (≥0.5 mm) are the primary source of inhibin in ovarian lymph.
• The ovarian lymphatic system serves as a potential route for inhibin to enter peripheral circulation.
• This study provides a validated method for inhibin measurement in sheep reproductive studies.