Effect of oestradiol on oxytocin-stimulated prostaglandin F2 alpha release in mares.

This study investigates the influence of a hormone, oestradiol, on luteal function in mares by evaluating its impact on the release of another hormone, prostaglandin F2 alpha, when stimulated by oxytocin. The findings establish that oestradiol significantly increased this release.

Objective and Methodology

• The primary focus of this study was to understand the role of the hormone oestradiol in luteal function. Luteal function refers to the activities and changes that occur in the corpus luteum, a temporary hormone-secreting structure in female mammals, during a reproductive cycle.
• The study examined how oestradiol affects the stimulation of 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM), a prostaglandin derivative, by oxytocin in cyclic mares. Cyclic mares refer to female horses in their regular reproductive or estrous cycle.
• The researchers conducted two different experiments. In the first, they administered 1 mg of two varieties of oestradiol (17 alpha and regular), or a non-medicated control substance to three groups of mares on specific days of their reproductive cycle followed by an intravenous oxytocin injection.
• The second experiment simulated a more physiological condition by inserting small spheres, impregnated with oestradiol into two groups of mares. These spheres released the oestradiol at a rate comparable to naturally occurring levels.

Results

• The findings suggested a significant stimulating effect of oestradiol on the oxytocin-induced increase of PGFM concentrations in cyclic mares. The impact was notably higher in comparison to the control group.
• However, there was no noticeable effect observed with the 17 alpha-oestradiol variant, suggesting that the stimulatory impact could be specific to the normal variant of oestradiol.
• Furthermore, the second experiment solidified these findings, showcasing a similar enhanced effect when a physiological dose of oestradiol was introduced directly into the uterus.

Conclusion

• Overall, the study provides evidence pointing to the role of oestradiol in enhancing the oxytocin stimulation of PGFM, thereby potentially influencing the luteal function in mares. However, further research is necessary to fully understand the mechanisms involved and potential implications for reproductive health in mares and potentially other mammals.