Progesterone responses to intravenous and intrauterine infusions of prostaglandin F2alpha in mares.

The research article investigates the movement of prostaglandin F2alpha (PGF) from the uterus to the ovaries in mares through a systemic route instead of a local route found in ruminants. It also explores the theory that one pulse of PGF results in only partial luteolysis.

Methodology

• Intravenous (i.v.) and intrauterine (i.u.) infusions of prostaglandin F2alpha (PGF) were done on mares 8 days after their ovulation. This was administered at a consistent rate for the duration of 2 hours.
• The researchers then observed the plasma concentrations of PGF by assaying 13,14-dihydro-15-keto-PGF2alpha (PGFM). Five different doses of PGF were used: 0, 0.05, 0.1, 0.5 and 1.0 mg for i.v., and 0 and 0.5 mg for i.u., with each group having four mares.
• Additionally, the research measured natural PGFM concentrations from samples collected each hour during luteolysis from five different pulses.

Results

• The researchers found that progesterone was similarly reduced 4 days after treatment in the 0.5 mg i.v., 0.5 mg iu., and 0.0 mg i.u. groups.
• The area under the PGFM curve in the 0.1 mg i.v. group was similar to the area for natural PGFM pulses.
• Progesterone decreased to a similar concentration in 12 hours in the 0.1, 0.5, and 1.0 mg i.v. groups, but remained greater in the 0.1 mg i.v. group afterward.
• Progesterone concentrations decreased to <2 ng mL(-1) 6 days after treatment in the 0.05 and 0.1 mg i.v. groups, and 2 days in the 0.5 and 1.0 mg i.v. groups.

Conclusion

• The research concluded that the results support the hypothesis of a systemic route for PGF transfer from the uterus to the ovaries in mares.
• They also concluded that one pulse of PGF results in only partial luteolysis in mares as opposed to full luteolysis, which contrasts with what happens in ruminants.