Estrogens and epididymal function

Estrogen is synthesized in the male reproductive system and is found in high concentrations in rete testis and seminal fluids. This luminal estrogen targets estrogen receptors (ER) along the male reproductive tract, and in particular the efferent ductules, where ERα is abundant. However, both ERα and ERβ are found in various regions of the male reproductive tract. The transgenic ER knockout mice (αERKO and βERKO) have been used to help define the role of ER in the male. In the αERKO animal model, the efferent ductules are dramatically altered, forming an epithelium in which fluid reabsorption is inhibited and epithelial cells have greatly reduced numbers of lysosomes and organelles associated with endocytosis. The βERKO male reproductive tract appears normal. Because these animals are transgenic and lack ER throughout development, we developed animal models using pure antiestrogen ICI 182,780 treatments in adult males. The data show that ERα participates in the regulation of the apical cytoplasm of non-ciliated cells of the efferent ductules, narrow cells of initial segment epididymis and clear cells in the remaining segments of the epididymis. There appears to be no effect on vas deferens. The inhibition of ERα function in the male leads to decreases in sperm concentrations and eventually to infertility. The current literature leaves the mechanisms of estrogen action in the male reproductive tract unsettled and raises the question of androgen's contribution to the regulation of fluid transport, especially in the efferent ductules.