Differential expression of steroidogenic enzymes by the primary corpora lutea of pregnant mares during equine chorionic gonadotrophin secretion.

This research article addresses how equine chorionic gonadotrophin (eCG) impacts the production of luteal androgen and oestrogen in pregnant mares. The study focuses on how eCG correlates with the expression of various steroidogenic enzymes at different stages of gestation.

Background of the Research

• The focus of this study is on equine chorionic gonadotrophin (eCG), a hormone produced in pregnant mares, which influences the production of luteal androgen and oestrogen.
• eCG levels increase exponentially from day 37 to day 60 of gestation and can be detected in the mother’s serum until about day 120-150 of gestation.
• Peak production of luteal androgen and oestrogen, stimulated by eCG, falls between 5 and 10 days after initial exposure to eCG, after which it gradually decreases. The research attempts to provide insights into how this process is regulated.

Methodology

• The researchers studied the mRNA expression of three key steroidogenic enzymes – 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450 17alpha-hydroxylase/17,20-lyase (P450(17alpha)) and cytochrome P450 aromatase (P450arom) in primary corpora lutea during different stages of gestation (before, during and after eCG secretion).
• This expression was determined using northern blotting, a technique used in molecular biology research to study gene expression.

Findings

• The expression of 3beta-HSD remained relatively unchanged at all stages that the research examined.
• The expression of P450(17alpha) increased at the onset of eCG secretion, decreased between days 42 and 46 of gestation, and remained constant for the rest of the eCG secretion period.
• Expression of P450arom was highest before and after eCG secretion and lowest during peak eCG secretion periods.
• The differential expression of P45017alpha and P450arom provides evidence that the production of luteal androgen and oestrogen is regulated by P450(17alpha) activity.
• The impact of eCG on the mRNA expression of these luteal steroidogenic enzymes appears to vary depending on the stage of gestation.