Steroidogenic enzyme activities in the pre- and post-parturient equine placenta.

The research investigates the activity of steroidogenic enzymes in equine placenta before and after birth. These enzymes are key to the production of specific hormone profiles, and the study found significant changes in enzyme activity near and at the point of birth, which could have implications for equine pregnancy and birth.

Understanding Steroidogenic Enzymes

• The study focuses on steroidogenic enzymes in the placentas of horses. These enzymes help to shape the profile of steroid hormones in the mother’s circulation during pregnancy.
• The enzymes include 3β-hydroxysteroid dehydrogenase/Δ5-4 isomerase (3βHSD) and 17α-hydroxylase/17,20-lyase cytochrome P450 (P450c17) which are important for the synthesis of progesterone and androgen respectively. Another key enzyme is aromatase cytochrome P450 (P450arom) which converts Δ4-androgens to estrogens.
• In the context of equine pregnancy, another important enzyme is 5α-reductase which helps to maintain pregnancy in the absence of progesterone during the second half.

The Part of 5α-reductase in Equine Pregnancy

• The activity and levels of 5α-dihydroprogesterone (DHP) and its metabolites decrease sharply just before birth, suggesting a role in the initiation of parturition.
• Despite the potential importance of this enzyme, few studies have investigated its activity in the placenta before and at parturition, which is the focus of this research.

Investigating Changes in Enzyme Activities

• Researchers observed key enzyme activities and transcript abundance in equine placentas at 300 days of pregnancy and post-birth.
• At 300 days, the placenta showed high levels of 3βHSD, 5α-reductase and aromatase, but minimal P450c17 activity when compared with the testis.
• By the time of foaling, the placenta showed unchanged 3βHSD and aromatase activities along with the unchanged transcript abundance, but 5α-reductase and P450c17 were no longer detectable. The transcript of 5α-reductase was also observed to decrease.

Conclusions of The Study

• The findings suggest that equine placentas have a substantial capacity for steroid metabolism by 5α-reductase, 3βHSD and aromatase, but limited capacity for androgen synthesis due to the lack of P450c17.
• There were noticeable changes in the pre-birth hormone concentrations, particularly the decline of 5α-reduced pregnane coincided with the loss of placental 5α-reductase activity and expression at the time of birth.
• This discovery could provide valuable insights into the hormonal control of births in horses and possibly lead to ways to manage or prevent equine birthing complications.