Ontogeny of uteroplacental progestagen production in pregnant mares during the second half of gestation.

This research investigates how the production of certain hormonal substances, called progestagens, by the uterine and placental tissues in pregnant horses, changes during the latter half of pregnancy. The study indicates that these changes may be important for successful pregnancy maintenance and timely commencement of labor.

Objective of the Research

• The purpose of this study is to evaluate the variations in the uteroplacental production of progestagens during the second half of gestation in pregnant mares. Progestagens are metabolites of progesterone, a hormone that plays a crucial role in maintaining pregnancy. The researchers aim to determine the amount, distribution, and rates of various specific progestagens produced in and around the uteroplacental unit. Understanding this could provide insights into mechanisms of how pregnancy is maintained and how labor is initiated in mares.

Methods Employed

• Eight specific progestagens were examined in this study, which was conducted on mares from the day 180 of pregnancy until term. The included mares were chronically catheterized, a procedure that allowed the researchers to monitor the progestagens level directly from the umbilical and uterine circulations.

Key Findings

• The researchers revealed no significant uptake of any of the eight progestagens from the uterine circulation. However, five of the examined progestagens demonstrated significant uptake from the umbilical circulation, with uptake levels rising as term approached.
• Two progestagens, 5 alpha-pregnane-3,20-dione (5 alphaDHP) and 20 alpha-hydroxy-5 alpha-pregnan-3-one (20 alpha 5P), were the primary outputs into both the umbilical and uterine circulations. Production of these two hormones increased as the term approached.
• The majority of the 20 alpha 5P was distributed into the uterine circulation, while 5 alphaDHP delivery switched from the uterus to the umbilical circulation after approximately 260 days of gestation.

Implications of the Findings

• The vertiginous rate of production and distribution of progestagens during the latter half of gestation could hold implications for how pregnancy is maintained and when labor is initiated in mares. The obtained results illustrate the essential role that progestagens play in the mare’s pregnancies, necessitating further studies to understand their deeper involvement in the birthing process.