Expression and localization of estrogen receptor α, estrogen receptor β and progesterone receptor in the bovine oviduct in vivo and in vitro

Abstract

This study examined the regulation and localization of estrogen receptors α and β (ERα, ERβ) and progesterone receptor (PR) in the bovine oviduct. Oviduct epithelial cells from cycling cows (in vivo) were investigated. In addition, the reactivity of a cell suspension culture stimulated with physiological doses of estradiol-17β (E2) or progesterone (P4) was tested (in vitro). The specific steroid receptor expression of oviductal cells was quantified for mRNA using real-time RT-PCR. Furthermore, steroid receptor proteins were analyzed by Western blotting and localized by immunohistochemistry in situ. Obvious cyclic changes of receptor expression in vivo were observed and concurrent expression patterns were detected in vitro. PR and ERα mRNA transcripts were elevated in vivo during the follicular phase. The highest PR and ERα protein expression was detected subsequently during the early-luteal phase. In vitro, E2-supplementation resulted in an upregulation of PR and ERα. Both ERβ mRNA and protein expression were highest during the luteal phase in vivo and elevated ERβ expression levels were observed in vitro after P4 treatment. Evidence is provided for a varying expression of ERα, ERβ and PR in bovine oviducts at different cycle stages in vivo, respectively under steroid supplementation in vitro. The region specific and cycle dependent expression differences point towards a functional importance of the three steroid receptors in the bovine oviduct, the site of fertilization and early embryonic development.