Effect of pregnancy and collection technique on prostaglandin F in the uterine lumen of Pony mares.

The research study investigates how pregnancy and various collection techniques affect concentrations of prostaglandin F (PGF) in the uterine lumen of Pony mares. The study also explores how treatments with estrogen, progesterone, or a prostaglandin synthase inhibitor, flunixen meglumine, affect PGF concentrations.

Methodology and Experimentation

• The researchers involved ovariectomized Pony mares and administered them subcutaneously with estrogen for one week and progesterone for two weeks.
• To collect uterine flushings, two methods were used, one by going through the cervix (Method A) and the other through the wall of the uterus post-hysterectomy (Method B).
• The research incorporated a phase where non-pregnant and pregnant mares were flushed on Day 14 post-ovulation and these flushings were compared with those from non-pregnant mares injected with flunixen meglumine, a prostaglandin synthetase inhibitor, within a short time frame before flushing.
• Uterine flushings were also collected from both non-pregnant and pregnant mares on Day 14 using the described techniques, and their endometrial and embryonic tissues were incubated both with and without flunixen meglumine.

Results and Observations

• In all experiments, pregnancy had a significant effect on PGF content of uterine flushings or incubation media, corroborating that gestation has a significant impact on intrauterine PGF levels.
• It was observed that flushings from pregnant mares had reduced PGF levels and were not influenced by the type of collection technique utilized.
• Non-pregnant Pony mares treated with progesterone responded with an increase in PGF concentration through cervical stimulation (Method A) compared to after hysterectomy (Method B).
• In terms of endometrial production of PGF, no effect was noted during a 2-hour incubation in Krebs-Ringer-bicarbonate buffer, whereas a 12-hour incubation showed significantly higher PGF output when the endometria were from pregnant mares versus non-pregnant mares.
• PGF production in vitro was significantly suppressed by flunixen meglumine, yolk sac membranes, and yolk sac and trophoblast, emphasizing the importance of these factors in modulating PGF production.

Conclusion

• The lower intrauterine PGF levels in pregnant mares and the lower in-vitro PGF production in the presence of the conceptus membranes might indicate inhibition of PGF synthesis and/or release prompted by the embryo.

This research thus provides valuable insights into the modulatory effects of pregnancy status and certain hormonal treatments, as well as collection methods, on uterine PGF concentrations.