Expression of estrogen receptor beta is developmentally regulated in reproductive tissues of male and female mice

By the use of ribonuclease protection assay (RPA) combined with immunohisto chemical techniques, the expression of estrogen receptor (ER) or and ERP wa s mapped in the developing gonads and reproductive tracts of male and femal e mice from fetal day 14 to postnatal day 26 (PND 26), This study was desig ned to determine the pattern of expression of both ER subtypes in specific tissue compartments during development. In ovaries, ER alpha mRNA was detec ted at all ages examined; ER beta mRNA was seen as early as PND 1, and its expression increased with age. Immunolocalization showed ER beta in differe ntiating granulosa cells of the ovary, whereas ER alpha was predominantly s een in interstitial cells. The remainder of the female reproductive tract s howed ER alpha mRNA at all ages examined with little or no significant leve ls of ER beta, except on END 1 when a low level of message appeared. In mal es, ER alpha and ERP mRNA were detected in the fetal testis; however, ER be ta gradually increased until PND 5 and subsequently diminished to undetecta ble levels by PND 26. Immunolocalization showed ER alpha in the interstitia l compartment of the testis, whereas ER beta was seen predominantly in deve loping spermatogonia, The remainder of the male reproductive tract showed v arying amounts of both receptors by RPA and immunostaining throughout devel opment. These studies provide information useful in studying the role of bo th ER subtypes in normal differentiation, and they provide indications of d ifferential tissue expression during development.