We examined the localization of oestrogen receptor (ER) β mRNA in the human endometrium throughout the menstrual cycle using non-radioactive in- situ hybridization with Brigati-tailed oligonucleotides. The findings were compared with those of ERα in order to examine the possible biological significance of ERβ in the human endometrium. Both ERα and ERβ mRNA expression were detected in all major human uterine cell types, including glandular epithelial cells, stromal cells and smooth muscle cells of the uterine wall, at every menstrual cycle stage. However, ERα mRNA expression was more prominent than that of ERβ in all cell types throughout the menstrual cycle. In proliferative phase endometrium, ERα mRNA was expressed in both glandular epithelial and stromal cells, while ERβ mRNA was expressed predominantly in glandular epithelial cells. Although the same pattern was observed in the secretory phase, both the ERα and ERβ mRNA expression was relatively weaker. These results suggest that oestrogenic effects occur predominantly through ERα, but that ERβ may also play a role in the modulation of oestrogenic action, especially on glandular epithelial cells in the human endometrium throughout the menstrual cycle.
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