Changes in equine endometrial oestrogen receptor alpha and progesterone receptor mRNAs during the oestrous cycle, early pregnancy and after treatment with exogenous steroids.

Two experiments were performed to determine changes in the abundance of oestrogen and progesterone receptor (ER alpha and PR) mRNAs in equine endometrium during the oestrous cycle and early pregnancy, and under the influence of exogenous steroids. In Expt 1, endometrial biopsies were obtained from non-mated mares during oestrus and at days 5, 10 and 15 after ovulation, and from pregnant mares at days 10, 15 and 20 after ovulation. There were overall effects of day on the abundance of ER alpha (P = 0.0001) and PR (P = 0.0014) mRNAs. The amount of ER alpha mRNA decreased at day 10 of pregnancy, and PR mRNA was reduced at day 5 in non-mated mares and at day 15 of pregnancy, compared with oestrous values. Experiment 2 was conducted to determine the effects of exogenous steroids on endometrial ER alpha and PR mRNAs. Endometrial biopsies were obtained from 19 anoestrous mares that had been treated with vehicle, oestradiol, progesterone, or oestradiol followed by progesterone for either a short or a long duration. The steroid treatment affected the abundance of ER alpha mRNA (P = 0.0420), which was higher (P < 0.05) in the oestradiol group than in the group treated with oestradiol followed by long duration progesterone. The steroid treatment did not affect the abundance of PR mRNA. These results demonstrate that the amount of steroid receptor mRNA changes with the fluctuating steroid environment in the uterine endometrium of cyclic and early pregnant mares, and that the duration of progesterone dominance may affect ER alpha gene expression. In addition, factors other than steroids may regulate ER alpha and PR gene expression in equine uterine endometrium.

[1]  Xiao Hong Ma,et al.  Regulation of the estrogen receptor and its messenger ribonucleic acid in the ovariectomized sheep myometrium and endometrium: the role of estradiol and progesterone. , 1996, Biology of reproduction.

[2]  K. Umesono,et al.  The nuclear receptor superfamily: The second decade , 1995, Cell.

[3]  K. M. Franklin,et al.  Changes in equine endometrial retinol-binding protein RNA during the estrous cycle and early pregnancy and with exogenous steroids. , 1995, Biology of reproduction.

[4]  G. H. Watson,et al.  Immunocytochemical localization and changes in endometrial progestin receptor protein during the porcine oestrous cycle and early pregnancy. , 1994, Reproduction, fertility, and development.

[5]  P. Poitras,et al.  Steroid synthesis by equine conceptuses between days 7 and 14 and endometrial steroid metabolism. , 1993, Domestic animal endocrinology.

[6]  B. Katzenellenbogen,et al.  Regulation of progesterone receptor gene expression and growth in the rat uterus: modulation of estrogen actions by progesterone and sex steroid hormone antagonists. , 1993, Endocrinology.

[7]  F. Bazer,et al.  Changes in progesterone and oestrogen receptor mRNA and protein during maternal recognition of pregnancy and luteolysis in ewes. , 1993, Journal of molecular endocrinology.

[8]  W. Fuller,et al.  Changes in Oestrogen Receptor Protein, mRNA Expression and Localization in the Endometrium of Cyclic and Pregnant Gilts , 1993 .

[9]  M. Tsai,et al.  Progesterone and estrogen , 1993 .

[10]  E. Watson,et al.  Progesterone and estrogen receptor distribution in the endometrium of the mare. , 1992, Theriogenology.

[11]  P. Sertich,et al.  Soluble oestrogen and progesterone receptors in the endometrium of the mare. , 1991, Journal of reproduction and fertility. Supplement.

[12]  R. Blair,et al.  Embryonic steroids and the establishment of pregnancy in pigs. , 2020, Journal of reproduction and fertility. Supplement.

[13]  P Chambon,et al.  Two distinct estrogen‐regulated promoters generate transcripts encoding the two functionally different human progesterone receptor forms A and B. , 1990, The EMBO journal.

[14]  M. Parker.  Mechanisms of action of steroid receptors in the regulation of gene transcription. , 1990, Journal of reproduction and fertility.

[15]  R. King.  Structure and function of steroid receptors. , 1987, The Journal of endocrinology.

[16]  K. Betteridge,et al.  Steroid secretion by different cell types of the horse conceptus. , 1987, Journal of reproduction and fertility. Supplement.

[17]  D. Sharp,et al.  Comparison of progesterone and progesterone + oestrogen on total and specific uterine proteins in pony mares. , 1987, Journal of reproduction and fertility. Supplement.

[18]  R. Roberts,et al.  Role of conceptus secretory products in establishment of pregnancy. , 1986, Journal of reproduction and fertility.

[19]  W. Okulicz,et al.  Hormone receptor control of pulsatile secretion of PGF2α from the ovine uterus during luteolysis and its abrogation in early pregnancy , 1984 .

[20]  K. Betteridge,et al.  Oestrogens and androgens in blastocoelic fluid and cultures of cells from equine conceptuses of 10-22 days gestation. , 1979, Journal of reproduction and fertility. Supplement.

[21]  F. Bazer,et al.  An investigation of the uterine luminal environment of non-pregnant and pregnant pony mares. , 1979, Journal of reproduction and fertility. Supplement.