Disruption of periovulatory FSH and LH surges during induced anovulation by an inhibitor of prostaglandin synthesis in mares.

This research examines the role of follicular fluid leakage during ovulation in the disruption of FSH and LH surges, in both ovulating and anovulating mares, triggered by an inhibitor of prostaglandin synthesis.

Research Context

• The study focuses on ovulation in mares, specifically how follicle-stimulating hormone (FSH) and luteinizing hormone (LH) surges around the time of ovulation (Periovulatory period) are influenced by the release of follicular fluid into the peritoneal cavity.
• This process was investigated in two groups of mares – ovulating and anovulating. The anovulation was triggered by treatment with an inhibitor of prostaglandin synthesis – a hormone involved in many body processes, including the reproductive cycle.
• An overview of the hormonal changes taking place around the time of ovulation can provide vital insights into reproductive processes and potential abnormalities in these processes.

Research Methodology

• The researchers used a sample size of 7 ovulating mares and 8 anovulating mares. The latter group was treated with an inhibitor of prostaglandin synthesis to block ovulation.
• The mares were pretreated with the hormone hCG when the largest follicle reached a size of 32mm and monitored closely using ultrasound scanning.
• The researchers collected blood samples at regular intervals from 24 to 60 hours after the pretreatment, closely following the changes in follicle size and hormone levels.

Results and Interpretation

• Until 36 hours post-pretreatment, both ovulating and anovulating mares showed similar follicle sizes and concentrations of FSH, LH, and estradiol-17β (a form of estrogen). However, between 34 and 36 hours, the blood flow in the follicular walls changed, and a new temporary increase in estradiol levels was observed.
• Disruptions in FSH and LH surges were noted in both groups, marked by a decrease or plateau between hours 38 and 48, and then a rise between 48 and 60 hours.
• The patterns observed suggested that the release of hormone-rich follicular fluid at ovulation was not the only factor affecting the change in FSH and LH levels around ovulation. The results proposed other potential routes for the inhibitors of these hormones from the follicle to the bloodstream, as the same disruption in hormone surges was observed in both ovulating and anovulating mares.