Expression of estrogen receptors in human corpus cavernosum and male urethra

Estrogen, largely produced in testis and adrenal gland, may play important roles in male reproduction. Most of the effects of estrogens are mediated by binding of estrogen to one or both of the two estrogen receptor (ER) subtypes alpha and beta. Recently, they have been described in testis, prostate, and efferent ducts, mostly in rodents. The goal of this study was to prove the evidence of ERs in human corpus cavernosum and male urethra, exploring the protein expression of these receptors by immunohistochemistry. Corpus cavernosum and corpus spongiosum smooth muscle was immunoreactive for the androgen receptor (AR), ERalpha, and strongly for ERbeta. Endothelial cells were negative for AR, sporadically positive for ERalpha, and positive for ERP. Urethral epithelium showed strong nuclear expression of AR, predominantly in the basal cell layer, and nuclear expression of ERalpha in the intermediate cells. ERbeta was highly expressed in almost all urethral nuclei and, much more weakly, in cytoplasm. Progesterone receptor (PGR) was negative in all cases and all tissues. These results represent the first report that ERalpha. and particularly ERbeta are regularly expressed in human penile tissue.