Physiologic and nonphysiologic effects of exogenous prostaglandin F2alpha on reproductive hormones in mares.

The study investigates the physiological and nonphysiological effects of administering Prostaglandin F2alpha (PGF), a substance involved in regulating reproductive hormones, in mares.

Research Methodology

• The experiment divided the subjects, mares, into three groups of four: a control group, which received no treatment; a bolus group, which was given a single 2.5 mg PGF treatment; and an infusion group, administered 0.1 mg of PGF over 2 hours.
• The researchers measured concentrations of 13,14-dihydro-15-keto-PGF2alpha (PGFM), progesterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and cortisol in the mares throughout the treatment period.

Research Findings

• The PGFM concentration in the infusion group was not significantly different from the natural PGFM pulse linked to luteolysis, the degradation of the corpus luteum – a temporary endocrine structure involved in reproduction.
• The bolus group exhibited increased progesterone levels initially, followed by a decrease over time, while the infusion group showed consistent drops in progesterone levels, further decreasing during 2 to 12 hours after the start of the treatment.
• The interval between ovulations was shorter in the bolus and infusion groups compared to the control group, indicating an accelerated reproductive cycle due to PGF treatment.
• The bolus group showed increased FSH, LH, and cortisol levels within 10 minutes of treatment, but no change was observed in the infusion group.

Study Implications

• The findings suggest that the rapid increase in progesterone, FSH, LH, and cortisol following a bolus treatment with PGF may not be physiologically normal.
• The researchers caution against conclusions on luteolytic mechanisms based solely on responses to a single bolus of luteolytic PGF treatment due to these nonphysiologic effects.