Serum progesterone and oxytocinase, and endometrial and luteal gene expression in pregnant, nonpregnant, oxytocin, carbetocin and meclofenamic acid treated mares.

The study examines how hormone levels and gene expression in pregnant and nonpregnant mares respond to various treatments, and how these factors are involved in pregnancy recognition and luteal function in horses.

Study Objective

The objective of the research was to assess changes in the expression of endometrial (lining of the uterus) and luteal (relating to the corpus luteum) genes during different stages of the reproductive cycle (estrus and diestrus), and how these expressions change during pregnancy and after certain treatments.

Procedure

• Groups of mares were defined based on their reproductive status or the treatment received: Diestrus (DIEST), Estrus (ESTR), Pregnant (PREG), Oxytocin (OXY), Carbetocin (CARB), and Meclofenamic acid (MFA).
• From day 12 to 15, blood samples were collected to measure the levels of oxytocinase (also known as leucyl-cysteinyl aminopeptidase or LNPEP) and progesterone.
• Luteal biopsies were taken on days 12 and 15, and endometrial biopsies on day 15.
• Real-time reverse transcription PCR (RT-PCR) was performed on the samples to measure the expression of specific genes pertinent to reproduction and pregnancy.

Key Findings

• Higher concentrations of serum LNPEP were observed in pregnant and oxytocin-treated mares than in diestrus mares.
• Endometrial PTGES expression, a gene involved in prostaglandin synthesis, was higher in diestrus, pregnant, and oxytocin-treated mares compared to other groups.
• Mares in estrus demonstrated increased expression of the OXT gene (oxytocin) compared to mares treated with MFA and oxytocin.
• Treatment with Carbetocin caused a decrease in the levels of serum progesterone and LNPEP, an increase in endometrial PLA2G2C, a decrease in endometrial PTGES, and a decrease in luteal aromatase and PTGES.
• Treatment with MFA resulted in decreased endometrial PLA2G2C, increased endometrial PTGES, and a lower abundance of luteal OXTR (oxytocin receptor) and OXT (oxytocin) on day 12 compared to day 15.

Conclusion

The researchers concluded that the levels of endometrial and luteal gene expression are governed by the physiological stage of the mare as well as the type of treatment administered. Most importantly, the protein LNPEP seems to play a crucial role in luteal function and pregnancy recognition in horses, affecting the synthesis of both oxytocin and prostaglandin.