Expression of the Arylhydrocarbon Receptor and the Arylhydrocarbon Receptor Nuclear Translocator during early gestation in the rabbit uterus

The arylhydrocarbon receptor (AhR) and the arylhydrocarbon receptor nuclear translocator (ARNT) are members of the PAS gene family mediating toxic eff ects of xenobiotics such as dioxin and polychlorinated biphenyls. We have a nalyzed the expression and cellular distribution of rabbit AhR and ARNT mRN A and protein level in the nonpregnant uterus and the pregnant and pseudopr egnant uterus at Days 6 to 12 of gestation. In the preimplantation uterus a t Day 6 of gestation and in the interimplantation and pseudopregnant uterus at Days 7, 8, 9, and 12 of gestation, low levels of AhR transcripts were d etected in the glandular uterine epithelium. Upon attachment of the blastoc yst at Day 7 of gestation, a strong expression of AhR and ARNT mRNA was obs erved in the luminal and glandular epithelium of the antimesometrial uterin e compartment. In contrast, AhR and ARNT expression was low in the luminal epithelium of the paraplacental and the mesometrial placental fold. AhR mRN A was also detected in the trophoblast cells. During early placentation at Day 9 of gestation, expression of AhR and ARNT was first observed in the pe rivascular decidualized stromal cells and, at Day 12, extended to the decid ualized stromal cells of the placental bed. Within the placenta, the syncyt iotrophoblast expressed only law levels of AhR and ARNT mRNA and no protein . The specific expression patterns of AhR and ARNT during early gestation s uggest functional roles for both transcription factors during fete-maternal interactions in the rabbit. (C) 1999 Academic Press.