Ovarian secretion of inhibin in mares.

This research investigates how ovarian hormones called inhibins change in mares (female horses) during ovulation, focusing particularly on where these hormones come from and how they are produced. The results indicate that their amounts increase during ovulation, particularly in larger follicles, which could explain the surge of these hormones during ovulation.

Research Methodology

• The researchers examined the concentration of compounds called immunoreactive inhibins during the process of ovulation in mares.
• The study focused on three sizes of ovarian follicles based on their respective diameters: small (30 mm).
• Immunohistochemistry was used to locate the inhibin alpha-subunit within ovarian follicles of all sizes. Inhibin betaA- and betaB-subunits were also detected.

Findings of the Study

• The study found that the inhibin alpha-subunit was localized to granulosa cells in follicles of all sizes and the theca cells of large follicles.
• Inhibin betaA- and betaB-subunits were found only in the granulosa and theca cells of large follicles.
• Large follicles contained high concentrations of three types of immunoreactive inhibin: inhibin, inhibin pro-alphaC, and inhibin A.
• Meanwhile, the concentrations of inhibin B were roughly the same in the follicular fluid of medium and large follicles.

Interpretation of the Results

• The study concluded that larger, mature follicles secrete high amounts of inhibin pro-alphaC and inhibin A.
• In contrast, smaller or medium follicles secrete limited amounts of inhibins A, B and pro-alphaC.
• The research implies that the high amounts of inhibin pro-alphaC produced by an ovulatory follicle is the source of the spike in concentrations of circulatory immunoreactive inhibin observed during ovulation.