Immunohistochemical localization of the estrogen receptor alpha (ERα) and progesterone receptor (PR) in the uterus of sika deer (Cervus nippon) during pregnancy

Abstract

Information on steroid hormone receptor distribution in the uterus is essential to understand the roles of their ligands in pregnancy. This study examined the spatio-temporal localization of estrogen receptor alpha (ERα) and progesterone receptor (PR) in the uterus of sika deer (Cervus nippon) to determine the estrogen and progesterone action site during pregnancy. Ovaries and uteri were collected from 21 pregnant sika deer with single fetus and two corpora lutea, ranging from Day 20 to Day 207 of pregnancy. In addition, genital organs were also collected from three sika deer whose gestational status was unknown: one female had only one developing corpus luteum: ≤ Day 4 (metestrus) and two females had two corpora lutea, one of which was at the developing stage equivalent to diestrus or early pregnancy: > Day 7 (diestrus). Staining of ERα and PR was clear in all cell types during metestrus. During diestrus, the presence of ERα was also clear in deep glandular epithelium, stroma and myometrium, whereas it was suppressed in luminal epithelium and shallow glandular epithelium. Staining of PR was suppressed in luminal epithelium but was detectable in other cell types. Staining of ERα in all cell types and PR in luminal epithelium and glandular epithelium became undetectable by Day 28. PR was presented in stroma and myometrium throughout pregnancy. The distribution pattern of ERα and PR was different during diestrus from that in a ruminant. This could be attributed to estrogen secretion from the maturing and ovulating follicles in the presence of developed corpus luteum