Distribution of estrogen receptors (ERα and ERβ) and androgen receptor in the testis of big fruit-eating bat Artibeus lituratus is cell- and stage-specific and increases during gonadal regression

The testis is a classical target for androgens, especially testosterone, acting via androgen receptor (AR). Alternatively, androgens can be aromatized to produce estrogens which act via specific receptors ERα and ERβ. Although estrogen action is essential for maintenance of male fertility, studies regarding the expression of ERα and ERβ in testis are restricted to a few species of rodent and domestic animals, but rarely in wild species. To our knowledge, there are no studies in Chiroptera species. Chiroptera represent one of the largest and most diversified orders of mammals, which possess several interesting reproductive features, including higher affinity of SHBG for estrogens than androgens. Therefore, we thought that bats would constitute a good model for investigation of the role of estrogens in the male. In this study, the distribution of ERα, ERβ and AR were evaluated in the testis of the big fruit-eating bat Artibeus lituratus and their levels were compared during reproductive and regressive periods. The results showed that ERα and AR were restricted to the somatic cells of the testis, whereas ERβ was widely distributed in both somatic and spermatogenic cells in a cellular and stage-specific fashion. We demonstrated for the first time by immunohistochemistry, and confirmed by Western blotting, that ERβ and AR increased during regression. The localization of ERα, ERβ and AR in a seasonal, cell and stage-specific fashion in the testis of A. lituratus suggests that these receptors may play important roles in testis function during reproductive and non-reproductive periods.