Prostaglandin E(2) and F(2 alpha) production by equine conceptuses and concentrations in conceptus fluids and uterine flushings recovered from early pregnant and dioestrous mares.

The research explores the production of Prostaglandins, particularly Prostaglandin E(2) and F(2 alpha), by equine conceptuses and its subsequent influence on the concentrations in conceptus fluids and uterine flushings in pregnant and dioestrous mares. Notably, the study finds that the equine conceptus suppresses the release of PGF(2 alpha) from the endometrium for maternal recognition of pregnancy.

Investigation into Prostaglandin Production

• The study performed measurements on the quantity and production process of PGF(2 alpha) and PGE(2) by equine conceptuses, with an age range from day 10 to day 32.
• It was discovered that the release of both prostaglandins per milligram of conceptus tissue was extremely high on the 10th day after ovulation, and lower on the days following.
• PGF(2 alpha) production experienced a further decrease after the 18th day of gestation, whereas, production of PGE(2) remained consistently high until day 32.

Prostaglandin Concentration in Various Components

• The research examined the concentration of prostaglandins in yolk sac fluid, the uterine lumen, and uterine flushings.
• Prostaglandin concentrations in yolk sac fluid were found to be stable, unaffected by gestational age. Interestingly, the concentrations of PGE(2) in this compartment were observed to be two to five times higher than the concentrations of PGF(2a).
• When analyzing PGF(2 alpha) concentrations within uterine flushings recovered from cyclic mares during the 14-16 days after ovulation, the time of expected luteolysis, researchers observed high values. However, these high values were nonexistent in flushings collected from pregnant mares during this same timeframe.
• After day 18 of gestation, PGF(2 alpha) concentrations in uterine flushings were high, notably similar to concentrations identified during cyclical luteolysis.

Findings and Conclusion

• The results suggest that the equine conceptus primarily affects maternal recognition of pregnancy by inhibiting the ability of the endometrium to release PGF(2 alpha) from days 12-16 after ovulation.
• The conceptus seems to delay the development of the uterine PGF(2 alpha) release pathway, rather than prevent its initiation. However, the researchers propose that there must be an alternative mechanism which prevents luteolysis from being activated between days 18-32 of gestation.