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

• Published in: Theriogenology 2018-03, Vol.108, p.185-191
• Main Authors: Maciel, L.F.S., Silva, E.S.M., Oliveira-Filho, J.P., Fritsch, S.C., Rossi, R.S., Lourenção, J.A.C., Meira, C.
• Format: Article
• Language: English
• Subjects: Anestrus; Equine; Hormonal protocols
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/j.theriogenology.2017.11.037

Administration of progesterone (P4) after estradiol is usually performed to prepare non-cyclic mares as embryo recipients. However, there are successful pregnancy reports after embryo transfer in non-cyclic mares treated only with progestins. The objective of this study was to evaluate endometrial gene expression and immunostaining for estrogen receptor alpha (ERα), beta (ERβ) and progesterone receptor (PR) in seasonal anestrous mares treated with long acting P4 (LA P4). Endometrial tissue from eight seasonal anestrous mares was collected immediately before administration of 1.5 g of LA P4 and five days after. The receptors protein expression was evaluated by immunohistochemistry and the percentage of the immunostained area was determined by ImageJ software. Transcripts abundance for ERα, ERβ and PR were determined by RT-qPCR. Blood samples were collected daily to measure plasma P4 concentrations. Protein expression for ERα was greater (p  0.05). There was no difference for ERβ protein expression (p = 0.07) and ERβ gene expression was reduced (p  0.05). In conclusion, endometrial PR and ERα expression patterns after LA P4 administration were similar to those previously found in protocols using estradiol prior to LA P4 to prepare non-cyclic mares as embryo recipients. •We evaluated endometrial expression for estrogen receptor α, beta and progesterone receptor in anestrous mares treated with long acting P4.•There was no variation for progesterone receptor and estrogen receptor α protein expression was increased after long acting P4 treatment.•There was no difference for estrogen receptor β protein expression, although the gene expression was reduced after treatment.•Results were similar to those previously found in protocols using estradiol prior to long acting P4 to prepare non-cyclic mares as embryo recipients.