Biological and immunoactive substances resembling chorionic gonadotropin are present in full-term horse and zebra placentas.

The research discovers that substances that act like Equine Chorionic Gonadotropin (eCG) are found in full-term placentas of horses and zebras.

Objective and Methods

• This research aimed at determining the presence of substances emulating the action of equine chorionic gonadotropin (eCG) in full-term placentas of horses and zebras.
• The researchers extracted term placental material which exhibited reaction in a luteinizing hormone (LH) monoclonal antibody radioimmunoassay (RIA).
• The techniques that had been used in the past for the purification of eCF and eLH were utilized in the study to further concentrate the reactive substances.
• The researchers then fractionated the horse material on a concanavalin A Sepharose column, resulting in an unadsorbed fraction named e17A and an adsorbed fraction, called e17B.
• The amount of zebra material obtained was however insufficient for this stage of the experiment.

Findings

• The final placental fractions, through high performance liquid chromatography (HPLC) gel filtration and LH immunoassays, showed a high degree of heterogeneity.
• Nonetheless, a distinct peak of immunoactivity was observed in one of the equine fractions (e17B) and in the insufficient zebra fraction (zD).
• HPLC gel filtration also established that e17B and z5D have a smaller molecular size than eCG or eLH. Yet, their size is almost similar to ovine (sheep) LH.
• e17B and z5D also exhibited bioactivity in the rat Leydig cell assay for LH, albeit low in potency compared to eCG or eLH. On the contrary, e17A was found to be inactive.
• However, e17A vastly cross-reacted in an eCG alpha RIA test, suggesting that it might be a partially formed or degraded alpha subunit.
• Radioimmunoassays (RIA) for LH, eCG, and eCG beta intimate that epitopes distinctive for these molecules are also likely present in the term placental materials or bear resemblance to them.