CHUNFA, W.; PATINO, R.*; DAVIS, K.B.: Cellular Distribution of Estrogen Receptor ALPHA and BETA Transcripts in the Testis of Channel Catfish

The cellular distributions of estrogen receptor ALPHA (ER-ALPHA) and ER-BETA in the testis have not been determined and compared in non-mammalian vertebrates. In this study, we examined the cellular distributions of ER-ALPHA and ER-BETA RNA in the testis of adult and juvenile channel catfish by in-situ hybridization. The cRNA probes used contained 5’-terminal end sequence that is specific for each receptor subtype. Tubules in the anterior region of the catfish testis contain the germinal elements, and in the adult fish examined the tubules were spermatogenic and had free sperm. Hybridization signal strength (antisense probe) for both receptor subtypes was low in primary spermatocytes and increased in secondary spermatocytes and spermatids. The most abundant signals for ER-ALPHA and ER-BETA RNA were observed in sperm. The presence of ER transcript in spermatogonia could not be determined since it was difficult to identify these cells in the hybridized tissue sections. Tubules in the posterior region of the catfish testis contain non-germinal columnar epithelium, and weak signals for ER-ALPHA and ER-BETA RNA were detected in the vicinity of the apical nuclei. The testes of the juvenile (pre-spermatogenic) catfish examined also showed signals for ER-ALPHA and ER-BETA RNA, preferentially in the stroma. In conclusion, ER-ALPHA and ER-BETA genes are both transcribed in the catfish testis and in the same cell types. Their transcripts are found preferentially in the germ cells of adult males and in the testicular stroma of juvenile males. Of particular interest is the high level of ER RNA content in sperm. These observations suggest that estrogens play important roles in the regulation of testicular physiology and spermatogenesis in channel catfish.