The role of PGE2 and PGF2a in follicle wall rupture and their implications in the development and treatment of luteinized unruptured follicles

Abstract

Summary:The article summarizes the results of several studies, which highlight the relevance of prostaglandins E2 (PGE2) and F2 (PGF2a) during the ovulatory process in mares and their implication in the pathogenesis of luteinized unruptured follicles. Following the preovulatory luteinizing hormone (LH) surge, the two prostaglandins are synthesized in granulosa cells. They subsequently trigger a cascade of events that lead to ovulation. The exogenous administration of intrafollicular PGE2 and PGF2a can induce follicle rupture and ovulation within 12 h of injection, even in mares in early estrus, and before the beginning of the abrupt rise of the preovulatory LH surge. The systemic administration of a prostaglandin synthesis inhibitor (flunixin-meglumine) during the periovulatory period blocks ovulation and induces the development of luteinized unruptured follicles (LUFs). LUFs share similar ultrasonographic and hormonal characteristics with hemorragic anovulatory follicles (HAFs). The administration of intrafollicular PGE2 and PGF2a in mares treated with a prostaglandin synthesis inhibitor restores normal ovulation and allows oocyte release and fertilization. However, the systemic administration of prostaglandins does not appear to have any effect on hastening ovulation.

Conception and early pregnancy in the mare: lipidomics the unexplored frontier

“…Interestingly, it has been shown that in the equine, COX2 gene expression in granulosa cells is a long molecular process, when compared to other species; appearing to be switched on approximately 30 h after the administration hCG for ovulation induction ( Boerboom & Sirois 1998 ). Prostaglandin synthesis, PGF 2α and PGE 2 have a role in follicular wall rupture and can be detected locally in equine follicular fluid ( Cuervo-Arango & Martìnez-Bovì 2016 ); no systemic increase in either of these lipids has been detected at ovulation. As oocyte expulsion must occur for natural fertilisation to take place, the interplay of many lipid hormones, at both local and systemic levels, is essential.…”