Biological functions and receptor binding activities of equine chorionic gonadotrophins.

This research article delves into the role of equine chorionic gonadotrophin (CG) in maintaining equine pregnancy. The researchers studied the effects of CG on maternal ovaries during early pregnancy, demonstrating that CG induces multiple secondary ovulations, ensuring necessary progestagen levels. They found that the growth of follicles resulting in secondary corpora lutea predates the secretion of CG. Additionally, certain pregnancy types stimulated mass follicular growth in addition to luteinization. The study further examined the binding activities of CG to its receptors, uncovering notably low binding affinity when horse CG binds to equivalent gonadal tissues of other species.

Role of Equine Chorionic Gonadotrophin

• In the study, the research team investigated the role of equine chorionic gonadotrophin (CG) in maintaining equine pregnancies. They found that CG helped ensure stifling maternal progestagen concentrations, crucial for sustaining the pregnancy.
• Interestingly, they observed that the growth of follies that lead to the creation of secondary corpora lutea often occurred before the secretion of CG itself, thus ruling the hormone out from being directly responsible for this particular process.

Impact of Different Pregnancies

• The research also noted varied impacts on follicular growth depending on the type of pregnancy. In donkeys carrying hinny pregnancies (a result of breeding a female donkey with a male horse), the CG produced by the hinny conceptus fostered significant follicular growth in addition to luteinization. This unique growth pattern may be linked to the enhanced sensitivity of donkey ovaries to ‘hinny CG’ which produces more FSH-like activity than normal donkey CG.

Receptor Binding Activities of CG

• Further in-vitro experiments were conducted to unearth the receptor binding activities of CG. Both horse and donkey gonadal tissues exhibited significantly low binding affinity to horse CG compared to the affinity exhibited by equivalent gonadal tissues in other species.
• The same horse CG bound modestly to horse LH receptors and donkey FSH receptors. However, it exhibited marginal binding when applied to horse FSH receptors.
• This pattern indicates a distinct receptor-mediated resistance to the gonadotrophic activities of the chorionic gonadotrophin in equids. The researchers suggest this might serve to protect the ovaries during pregnancy, preventing any potential hormonal overwhelm.