Localization of estrogen and androgen receptors in male reproductive tissues of mice and rats

Using immunohistochemical methods, we studied the cell-type- and species-specific expressions of estrogen receptor (ER) isoforms (ERalpha and ERbeta) and androgen receptors (ARs) in the male reproductive tract and accessory sex glands of mature mice and rats. ERalpha and ERbeta showed cell-type- and species-specific distributions, respectively. In contrast, AR was localized in the epithelial and stroma cells of all tissues examined in this study, in both species. In mice, the epithelial cells of the ductuli efferentes showed a strong ERalpha-immunoreaction, and those of the caput epididymis, coagulating glands, and prostate also exhibited a positive reaction. Stroma cells, except in the ductuli efferentes, showed a positive ERalpha-immunostaining. In rats, ERa was detected in very few cell types: the epithelial cells of the ductuli efferentes showed a strong reaction, and the stroma cells of the ampullary and urethral glands exhibited a weak reaction. ERbeta was localized in the epithelial cells of the prostate in mice, while the reaction was faint or negative in both the epithelial and stroma cells of other tissues. In rats, the ERbeta-immunoreaction was strongest in the epithelial cells of the ventral prostate. The epithelial cells of the corpus and cauda epididymis, ductus deferens, and urethral glands, and the stroma cells of the urethral glands were also positively ERbeta-immunostained. Almost the same AR distribution pattern was observed in both species. In particular, strong AR-immunostaining was present in the epithelial cells of the caput and corpus epididymis, seminal vesicle, and ventral prostate. These results indicate that species and tissues differences should be taken into careful consideration in assessing the physiological and pharmacological effects of sex steroids (particularly estrogens) on the reproductive tissues of male rodents. (C) 2004 Wiley-Liss, Inc.