The presence of 19-norandrostenedione and its sulphate form in yolk-sac fluid of the early equine conceptus.

This study identifies and examines the presence of a specific steroid, 19-norandrostenedione, and its sulphate form in an early-stage horse fetus’ yolk-sac fluid. The significance of this steroid’s high levels found in the fluid remains unknown but seems to correspond with the activity levels shown in the pig and horse blastocyst for an enzyme involved in steroid production, P450 aromatase.

Objective and Methodology

• This research aims to identify and quantify the specific steroid forms in the yolk-sac fluid of early equine conceptuses.
• The researchers previously detected large amounts of androgens in the yolk-sac fluid and used Radioimmunoassay (RIA), a technique to measure antigens, to tentatively identify the predominant androgen as norandrostenedione, not androstenedione.
• They also suspected an even more substantial quantity of norandrostenedione was present as a sulphoconjugate, identified using extraction, solvolysis, high-performance liquid chromatography (HPLC), and RIA.

Findings

• The findings were validated with further purification using two high-performance liquid chromatography (HPLC) systems and definitively identified by liquid chromatography-mass spectrometry (LC-MS) with an authentic standard of 19-norandrostenedione.
• Moreover, the initial extraction of the steroid sulphate as a methylene-blue complex also yielded 19-norandrostenedione, suggesting the 3-enol form had enabled sulphoconjugation.

Implication and Further Questions

• It remains uncertain why the sulphate form is retained within the fluid; however, the high amounts of 19-norandrostenedione found in the fluid are consistent with reports on the catalytic activity displayed in vitro by the horse and pig blastocyst isozyme of P450 aromatase.
• The P450 aromatase enzyme is known for its role in producing estrogens, a type of steroid hormone. Therefore, this correlation suggests the yolk-sac fluid may play a crucial role in the steroid production of the early-stage fetus.
• This research serves as a basis for further investigation into this phenomenon’s biological significance and potential implications for equine fetal development.