Expression of Estrogen Receptors (alpha)and (beta) in the Fetal Baboon Testisand Epididymis

Although studies in transgenic mice suggest that estrogen is important for development of the testis, very little is known about the potential role of estrogen in maturation of the primate fetal testis. Therefore, as a first step to determine whether estrogen regulates maturation of the fetal primate testis, we used immunocytochemistry to determine estrogen receptor (ER)(alpha) and (beta) expression in the fetal baboon testis. Second, we established methods to quantify ER(beta) mRNA levels by competitive reverse transcription-polymerase chain reaction in Sertoli cells isolated by laser capture microdissection (LCM) from the fetal baboon testis. ER(beta) protein expression was abundant in the nuclei of Sertoli, peritubular, and interstitial cells in baboon fetuses at mid (Day 100) and late (Day 165) gestation (term is 184 days). ER(beta) mRNA level was 0.03 attomole/femtomole 18S rRNA in Sertoli cell nuclei and associated cytoplasm isolated by LCM. ER(alpha) was expressed in low level in seminiferous tubules and in moderate level in peritubular cells on Day 165. Germ cells expressed very little ER(alpha) or ER(beta) protein, whereas the baboon fetal epididymis exhibited extensive ER(alpha) and ER(beta) immunostaining at mid- and late gestation. In contrast to the robust expression of ER(beta), androgen receptor protein was not demonstrable within the cells of the seminiferous cords but was abundantly expressed in epididymal epithelial cells of the fetal baboon. In summary, the results of this study show that the fetal baboon testis and epididymis expressed the ER(alpha) and ER(beta), and we suggest that our nonhuman primate baboon model can be used to study the potential role of estrogen on maturation of the fetal testis.