Gonadotropin-dependent regulation of the prostaglandin E2 receptor in equine preovulatory follicles during the ovulatory process in mares.

This research focuses on investigating how the ovulation process in mares, specifically the regulation of the prostaglandin E2 receptor subtype 2 (PTGER2), is affected by gonadotropin. The researchers found that the receptor PTGER2 and its molecule prostaglandin E2 play an important role in ovulation and are upregulated by the presence of gonadotropins.

Main Objectives of Study

• The study aimed to clone the primary structure of the prostaglandin E2 receptor subtype 2 (PTGER2) cDNA. This includes understanding the role PTGER2 plays in the ovulatory process.
• The researchers also hoped to characterize the regulation of PTGER2 in equine follicles, specifically during gonadotropin-induced ovulation.

Late Ovulation Stages

• The researchers observed the regulation of PTGER2 by conducting semi-quantitative RT-PCR/Southern blot experiments. These occurred on preparations of theca interna and mural granulosa cells, isolated from equine follicles at various points post-treatment with human chorionic gonadotropin (hCG).
• The results showed a significant increase in PTGER2 mRNA at 24 and 39 hours post-hCG in granulosa cells and at 30 and 33 hours post-hCG in theca cells.

Protein Presence

• Immunohistochemical staining and immunoblotting performed on equine follicular samples showed a corresponding increase of PTGER2 protein in both cell types after hCG treatment, supporting that hCG induced the expression of PTGER2.

Additional Observations

• Levels of PTGER2 mRNA were also high in uterus, thymus, and spleen, but moderate to low in other tested tissues, indicating its role isn’t confined to the ovarian environment.
• The researchers observed the expression of another prostaglandin receptor (PTGER4) mRNA in granulosa cells, which was most abundant at 12 and 39 hours post-hCG, suggesting its potential involvement in ovulation as well.

Conclusion

• This study is the first to report that in mares the ovulatory process includes a gonadotropin-dependent up-regulation of PTGER2 and PTGER4. Prostaglandin E2 receptor might help regulate the preovulatory effects of prostaglandin.