Hormone concentration changes temporally associated with the hour of transition from preluteolysis to luteolysis in mares.

This research study investigates the time-specific changes in the levels of cortisol, estradiol-17β, and oxytocin in mares that are related to the transition from preluteolysis to luteolysis.

Overview of the Study

• This study aims to unravel the relationship and time-bound changes of different hormones i.e., cortisol, estradiol-17β, and oxytocin with pulses of prostaglandin F metabolite (PGFM), especially during the hour of transition from preluteolysis to luteolysis in mares.

Methodology

• The researchers utilized hourly blood samples from mares and focused on the concentration changes of these hormones.
• The transitional hour, the timeframe wherein the change from preluteolysis to luteolysis occurs, was deduced from progesterone concentrations.
• For all horses involved in the study, this hour consistently occurred between 2 PM and 2 AM.
• Researchers then categorized PGFM pulses into preluteolytic, transitional, and luteolytic pulses.

Results and Interpretation

• The findings reported that the preluteolytic and transitional pulses of PGFM were less prominent compare to the first luteolytic pulse. This was determined through concentration measurements.
• It was discovered that cortisol levels rose just before the peak of the luteolytic PGFM pulse and then fell during the hours of the pulse, but no similar changes were observed during preluteolytic and transitional pulses.
• Estradiol’s concentration increased in the hours leading up and following the luteolytic pulse, but did not demonstrate the same behavior for other pulses.
• Interestingly, oxytocin concentrations differed during the transitional and the luteolytic PGFM pulse but it didn’t show significant change during the hours of the last preluteolytic pulse.
• Oxytocin records showed an increase leading up to the transitional and the luteolytic pulses, and a subsequent fall.
• The alterations in oxytocin concentrations were considered noteworthy, and led to the hypothesis that oxytocin, in tandem with PGF2α, is responsible for the transition from preluteolysis to luteolysis within a single hour in mares.

Conclusions

• The research outcomes support previous theories about hormonal influence on reproductive processes and present novel insights specifically about the temporal associations of oxytocin levels on the transition from preluteolysis to luteolysis in mares.