Seasonal variation in estrogen receptor ERα, but not ERβ, 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 ER alpha (ESR1) and ER beta (ESR2). ER alpha has been found in the ED of all species studied so far. However, in the epididymis (EP), the expression of ER alpha 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, ER alpha, ER beta and AR in the ED and EP of A. lituratus was investigated. The results showed that aromatase, AR and ER beta were distributed throughout the excurrent ducts and did not vary during the annual reproductive cycle. Conversely, ER alpha 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 ER alpha 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 ER alpha, which is similar to previous findings in animals lacking functional ER alpha. (C) 2012 Elsevier Inc. All rights reserved.