Steroid content of the equine ovary during the reproductive cycle.

The research article explores the steroid content present in a horse’s ovary during its reproductive cycle. Through the examination of follicular fluid and corpora lutea from nine mares, the primary steroid was identified as oestradiol, with significant levels also detected after ovulation.

Investigation of Equine Ovaries During Reproduction Cycle

• The study examined follicular fluid, which is a liquid that resides in every ovarian follicle in female bodies, but in this case, that of mares.
• Nine female horses (mares) in their menstrual cycle were used for the extraction of the follicular fluid.
• The fluid was then subjected to gas-liquid chromatography, an analytical technique used to separate and measure volatile substances, to determine the concentration of different steroids.

Key Findings from the Steroid Concentration Analysis

• The steroids detected in the follicular fluid from the ovaries included progesterone, 17α-hydroxyprogesterone, androstenedione, 19-norandrostenedione, epitestosterone, oestrone, and oestradiol.
• The most vascular follicles, likely those intended for ovulation, typically exhibited the highest concentrations of these steroids.
• The predominant steroid found in these highly vascular follicles was oestradiol with an average concentration of 151 μg/100 ml.

Steroids Present Following Ovulation

• Upon evaluating the follicular fluid obtained from mares with recent ovulations, large amounts of oestradiol were detected.
• The corpora lutea (yellow body formed in the ovary following ovulation) from these mares included steroids such as progesterone, 17α-hydroxyprogesterone, 20α-dihydroprogesterone, and pregnenolone.
• It’s worth noting that pregnenolone was not found in any follicular fluid samples.

Corpora Lutea and Steroid Content

• Upon analyzing a pool of eight mid-cycle corpora lutea, the same four steroids were detected as those in newly-formed bodies.
• However, oestradiol was also present, estimated around 4 μg/100 g.