Endometrial expression of estrogen and progesterone receptors in non-cyclic mares treated only with long-acting progesterone.

The study investigates the effect of long-acting progesterone (LA P4) on the endometrial expression of estrogen and progesterone receptors in non-cyclic mares, finding that treatment with LA P4 alone can mimic the effects of estradiol-preceding protocols used to prepare non-cyclic mares for embryo implantation.

Objective of the Research

• The primary purpose of this study was to examine the endometrial gene expression and immunostaining for the estrogen receptors ERα and ERβ, and the progesterone receptor (PR), in seasonal anestrous mares treated with long-acting P4.

Research Methodology

• The researchers collected endometrial tissue from eight seasonal anestrous mares both immediately before and five days after the administration of 1.5 grams of LA P4.
• The expression of the receptors’ proteins was evaluated using immunohistochemistry. The percentage of the immune-stained area was determined using ImageJ software.
• The abundance of transcripts for ERα, ERβ, and PR was determined with RT-qPCR. Blood samples were collected daily to measure the plasma P4 concentrations.

Research Findings

• The study found that the protein expression for ERα increased significantly after LA P4 administration, but the gene expression did not change due to this treatment.
• No significant difference was found for ERβ protein expression, while a notable decrease was noted in ERβ gene expression following the treatment.
• The gene and protein expression for PR did not experience any changes.

Conclusion

• The study concluded that administering LA P4 to seasonal anestrous mares resulted in similar endometrial PR and ERα expression patterns to those observed in protocols where estradiol is used prior to LA P4 to prepare non-cyclic mares for embryo transfer.