Localization of estrogen receptor alpha and beta RNA in germinal and nongerminal epithelia of the channel catfish testis

The germinal epithelium of the anterior region of the channel catfish testi s is the site of spermatogenesis, whereas the nongerminal epithelium of the posterior region (seminal vesicle) may play a role in the regulation of se minal fluid composition. The available information indicates that estrogens play a physiological role in the regulation of spermatogenesis and seminal fluid composition in vertebrates. However, the cellular distribution of es trogen receptor (ER) gene expression in the teleost testis is poorly unders tood. Therefore, the objective of this study was to determine the presence and cellular distribution of ER alpha and ER beta transcripts in germinal a nd nongerminal epithelia of the mature testis of channel catfish. RT-PCR of whole-testis RNA extracts showed that ER alpha and ER beta RNAs are presen t in the mature testis. In situ hybridization of histological sections of t he germinal epithelium showed that primary spermatocytes contain little or no ER alpha or ER beta RNA. However, both ER transcripts were present in se condary spermatocytes and spermatids and their levels were relatively high in mature sperm, The columnar epithelium of the seminal vesicle also contai ned ER alpha and ER beta RNA. The ER RNAs in epithelial cells of the semina l vesicle were not evenly distributed throughout the cytoplasm but seemed t o concentrate in their apical region, near the nucleus. In conclusion, ER a lpha and ER beta genes are coexpressed in germinal and nongerminal epitheli a of the mature testis of channel catfish and seem to be developmentally re gulated in spermatocytes. These observations are consistent with the concep t that estrogens, via interaction with ER alpha and ER beta, participate in the regulation of male gamete development and fertility. (C) 2001 Academic Press.