Androgen receptor expression in the testes and epididymides of prenatal and postnatal Sprague-Dawley rats

The androgen receptor (AR) plays a critical role in sexual differentiation and in the virilization of the male reproductive system. A clear understand ing of AR expression at the early stages of sexual development will help el ucidate the sensitivity of perinatal animals to endocrine modulation by ext ernal agents, such as some environmental chemicals. Immunohistochemistry wa s used in this study to localize the AR in the differentiating testis and e pididymis of Sprague-Dawley rats starting from gestation day 15 until postn atal day 21, Positive AR staining was found on gestation day 15 in the mese nchymal as well as in the epithelial cells in the mesonephros. Weak stainin g was also observed in a small number of interstitial cells in the primordi al testis at this age. The fetal interstitial and peritubular myoid cells s howed positive AR immunoreactivity early in development, but the Sertoli ce lls did not overtly express the receptors until postnatal day 5, The intens ity of staining and number of AR-positive cells in the testis and epididymi s increased over time. The epithelium in the mesonephros-derived tissues, i ncluding rete testis and epididymis, appeared to exhibit a higher capacity to express AR than the rest of the testicular tissue. The results demonstra te that AR expression in the primordial male reproductive system is highly specific to time and cell type and modify previous understanding on the tim ing of AR expression in the testicular tissue, Since AR-positive cells at v arious developmental stages may be potential sites of interaction with chem icals that adversely affect sexual differentiation, improved understanding of AR ontogeny will help in investigating the effects of AR-reactive agents , such as environmental antiandrogens, with respect to specific windows of sensitivity.