Oestrogen receptors in the human and primate testis and reproductive tract

Abstract

The impact of oestrogens on the male reproductive system remains the subject of intensive research activity and debate. Oestrogen action is mediated via high affinity intracellular receptors expressed in target tissues. Two subtypes of oestrogen receptor known as ERα (NR3A1) and ERs (NR3A2) have been cloned and hERs variant isoforms identified. In target cells these receptors can exist as homoor heterodimers. We have used immunohistochemistry to examine the patterns of expression of ERs in human and non-human primates as a first step in determining the cellular targets for oestrogen action in the male. ERα was detected in the epithelial cells of efferent ductules (ED) occasionally in epithelial and stromal cells within the epididymis but was undetectable in human or primate testes. Using a polyclonal antibody raised against the hinge domain of ERs, immunopositive staining was detected in multiple cell types within the testis and in epithelial and stromal cell nuclei throughout the male reproductive system (ED, epididymis, vas deferens, seminal vesicles, prostate) and in the bladder. We have also used monoclonal antibodies that distinguish between wild type, full-length ERs (ERs1), and a splice variant isoform called ERscx/ERs2 that does not bind oestrogens. ERs1 and ERs2 proteins were both detected in human testis and have distinct but overlapping patterns of expression. ERs1 was also detected in ED, epididymis and vas. In conclusion, oestrogen receptors are widely expressed in the male urogenital system and with the exception of the ED there are more cells that express ERs than ERα. In the adult human the testicular cells most likely to be targets for oestrogens are round spermatids in which levels of expression of full-length wild type receptor (ERs1) are high.