Estrogen metabolites in equine ovarian follicles: gas chromatographic-mass spectrometric determinations in relation to follicular ultrastructure and progestin content.

The study involves the evaluation of estrogen metabolites within the ovarian follicles of horses using gas chromatographic-mass spectrometry, comparing results in relation to the follicle’s stage of development and progestin content.

Objective of the Study

• The research aimed at a comprehensive investigation of estrogen metabolites within the ovarian follicles at different developmental stages [viable (healthy), preovulatory (just before release of the egg), and atretic (degenerating)] of horses. Moreover, the study analyzes those findings against the follicle’s ultrastructure and its progestin (a type of hormone) content.

Methodology

• Gas chromatography-mass spectrometry was employed to examine the presence and quantity of estrogens and progestins in equine follicular fluid. This method allows for high precision in identifying and analyzing chemical substances within a sample.
• A technique known as stable isotope dilution was used in conjunction with gas chromatography-mass spectrometry, providing further accuracy in quantifying the levels of hormones.
• The study included studying the ultrastructure of the follicles at various developmental stages. This methodology implies a detailed study of its structure at microscopic level.

Results

• Among the examined progestins, progesterone and 17-hydroxyprogesterone were found to be the main hormones in preovulatory and viable follicles. Progestins are essential for maintaining pregnancy in mares, and these two forms are particularly significant during the lead up to ovulation.
• When looking at the catechol estrogens, 2-hydroxy-estradiol was found to be highly abundant in the preovulatory follicle, indicating its possible importance in the ovulation process.
• Specific identification of 2-hydroxy-estradiol was confirmed by scanning a full mass spectrum, which is a plot of the ion signal as a function of the mass-to-charge ratio. This provides definitive identification of the chemical substances involved.