mibolerone and 11-ketotestosterone

We have recently isolated two androgen receptor cDNA clones from the rainbow trout testis. To investigate the functions of the rainbow trout androgen receptor-alpha (rtAR-alpha), we investigated the ligand binding ability and transcriptional activity of rtAR-alpha. Interestingly, in ligand-competition experiments, testosterone (T) (IC(50) 3 x 10(-9) M) competed with [(3)H]mibolerone binding for rtAR-alpha slightly more potently than the teleost fish-specific natural androgen 11-ketotestosterone (11KT) (IC(50) 8 x 10(-9) M), which is thought to be the functional spermatogenesis inducer. In contrast, T (EC(50) 5 x 10(-9) M) and 11KT (EC(50) 6 x 10(-9) M) showed similar efficiency upon cotransfection into EPC cells with a rtAR-alpha expression vector and an androgen-responsive element-based reporter gene. These results indicated that activation of rtAR-alpha does not distinguish between 11KT and T and suggested that a specific system, which is mediated only by 11KT, may exist in the rainbow trout.

Topics: Androgens; Animals; Cells, Cultured; Cloning, Molecular; Cytosol; Immunoblotting; Kinetics; Ligands; Male; Nandrolone; Nuclear Receptor Coactivators; Oncogene Proteins; Oncorhynchus mykiss; Receptors, Androgen; Spermatogenesis; Testis; Testosterone; Testosterone Congeners; Trans-Activators; Transcription Factors; Transcriptional Activation