Arylhydrocarbon receptor (ahr)‎ expression in bovine ovary and uterus during estrous cycle and early pregnancy : an immunohistochemical study

الملخص EN

ABSTRACT The arylhydrocarbon receptor (AhR) is a ligand activated transcription factor.

The AhR was found in embryos, fetuses and in genital tract tissues of some lab animals and human; However, Its role in reproduction and fertility in different species is still to be elucidated.

By employing immunohistochemistry in the current study, AhR expression was studied in bovine ovary and uterus in cyclic and early pregnant cows .

In the ovary; during estrous, AhR was expressed in the stromal (interstitial) cells while in diestrous and early pregnancy it was found in luteal and stromal cells.

In the uterus, during diestrous, the receptor was always expressed in connective cells and in the endometrial epithelium showing localized cytoplasmic staining apical to the nucleus; nuclear staining was only observed in the uterine glands.

During estrous, the receptor was only localized in the connective tissue cells while the epithelium was immunonegative.

In the uterus at day 13 of early pregnancy, similar staining pattern as with diestrous was recorded.

Myometrium was always immunonegative.

Estrogen is essential factor for establishment of normal pregnancy in mammals.

Estrogenic action in uterus was found to be mediated by intracellular, primarily nuclear receptor called estrogen receptor-alpha (ER-?).

In the current study; immunohistochemistry was used to localize ER-? in the uterus of pregnant and psudopregnant rabbits.

ER-? was strongly expressed in non pregnant uteri in nearly all cellular compartments as luminal and glandular epithelium, stromal cells and myometrial smooth muscle cells.

Marked down regulation of the ER-? in luminal but not in glandular epithelium was observed during early periods of pregnancy and pseudopregnancy.

Weaker glandular staining was only observed during postimplantation periods.

Stromal cells were always immunopositive even after implantation till day twelve of pregnancy.

Myometrium was expressing the receptor till after implantation.

ER-? was always nuclear in immunopositive cells.

Our results revealed that, ER-? was involved in the process of progestational proliferation in the rabbit uterus; in addition, the receptor expression is tissue specific and maternally controlled.