IMMUNOLOCALIZATION OF ESTROGEN RECEPTOR-ALPHA WITHIN THE TESTIS AND EXCURRENT DUCTS OF THE RAT AND MARMOSET MONKEY FROM PERINATAL LIFE TO ADULTHOOD

The sites of action and the physiological role of oestrogens in the ma le reproductive tract are poorly understood. We have undertaken a syst ematic study of the immunoexpression of oestrogen receptor-alpha (ER a lpha) in the male rat from late fetal life through to adulthood and co mpared the findings with results obtained in the marmoset monkey (Call ithrix jacchus) from neonatal to adult life. The testes, rete testis, efferent ducts and epididymis were examined from normal male rats (age d 4, 8, 10, 15, 20, 25, 38, 48 and 90 days) and from male rat fetuses on days 17.5 and 18.5 of gestation; comparable tissues were examined f rom neonatal, infantile, peripubertal and adult marmosets aged 8, 18-2 4, 54-62 and 92-112 weeks respectively. Immunolocalisation of ER alpha used antigen retrieval and a monoclonal antibody directed to the N-te rminus, which had proved superior to six other antisera tested. ER alp ha was immunoexpressed in interstitial cells, including the fetal/neon atal generation of Leydig cells, in both the rat and marmoset. In the rat, the adult generation of Leydig cells were also immunopositive for ER alpha whereas the comparable cells in the marmoset were only weakl y immunopositive. ER alpha was not expressed in Sertoli cells, peritub ular myoid cells, blood vessels or germ cells at any time in either sp ecies. In late fetal life in the rat, ER alpha was immunoexpressed in cells surrounding the mesonephric tubules, whereas postnatally it was expressed in the epithelium of the rete testis and efferent ducts at a ll ages from 4 to 90 days; this immunoexpression was most pronounced i n the efferent ducts. In the marmoset, the efferent ducts, but not the rete testis, also showed intense immunoexpression of ER alpha. Apart from sporadic immunostaining for ER alpha in the epididymal duct of th e rat in the neonatal period, the caput, corpus and cauda epididymis w ere negative for immunoexpression of ER alpha at all ages in both spec ies. These findings suggest that the main actions of oestrogens in the male reproductive tract, mediated by ER alpha, are related to the dev elopment and function of the efferent ducts and the Leydig cells. In c onsideration of data from this and previous studies of oestrogen bindi ng, we predict possible sites of expression of other oestrogen recepto rs (e.g. ER beta) in Sertoli cells and the epididymis. Interactive eff ects, related to the relative levels of androgens and oestrogens, coul d be physiologically important in the excurrent ducts of the adult tes tis.