Seasonal variation in estrogen receptor ERα, but not ERß, androgen receptor and aromatase, in the efferent ductules and epididymis of the big fruit-eating bat Artibeus lituratus.

The efferent ductules (ED) are a major target for estrogens, which act via the estrogen receptors ERα (ESR1) and ERß (ESR2). ERα has been found in the ED of all species studied so far. However, in the epididymis (EP), the expression of ERα is controversial, as is data about the occurrence of aromatase in the epithelium lining the excurrent ducts. Therefore, to further investigate this estrogen-responsive system, we used a seasonal breeder, the Neotropical bat, Artibeus lituratus, in which testicular expression of androgen (AR) and estrogen (ER) receptors vary with reproductive phase. The localization of aromatase, ERα, ERß and AR in the ED and EP of A. lituratus was investigated. The results showed that aromatase, AR and ERß were distributed throughout the excurrent ducts and did not vary during the annual reproductive cycle. Conversely, ERα was detected primarily in the ED epithelium, had marked seasonal variation and was increased during regression, especially in the EP epithelium. The results suggest that ERα may be involved in preparing the male genital tract for recrudescence. Together, the data obtained under natural conditions emphasize that specific segments of the excurrent ducts downstream of the testis are the primary targets for estrogen action via ERα, which is similar to previous findings in animals lacking functional ERα.