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

This study examined the regulation and localization of estrogen receptors alpha and beta (ERalpha, ERbeta) 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-17beta (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 ERalpha mRNA transcripts were elevated in vivo during the follicular phase. The highest PR and ERalpha protein expression was detected subsequently during the early-luteal phase. In vitro, E2-supplementation resulted in an upregulation of PR and ERalpha. Both ERbeta mRNA and protein expression were highest during the luteal phase in vivo and elevated ERbeta expression levels were observed in vitro after P4 treatment. Evidence is provided for a varying expression of ERalpha, ERbeta 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. (C) 2003 Elsevier Science Ltd. All rights reserved.