Nonylphenol modulates expression of androgen receptor and estrogen receptor genes differently in gender types of the hermaphroditic fish Rivulus marmoratus

To uncover the effect of estrogenic chemicals [4-nonylphenol (NP) and bisphenol A (BisA)] on the expression of androgen receptor (AR) and estrogen receptors (ER alpha and ER beta) in the hermaphroditic fish Rivulus marmoratus, we cloned the full length of the cDNAs encoding AR, ER alpha, and ER beta from gonadal tissue of R. marmoratus and analyzed the modulation of expression of these genes following exposure to estrogenic chemicals using real-time RT-PCR. R. marmoratus AR, ER alpha, and ER beta genes showed a high similarity to the relevant fish species on amino acid residues, respectively. Rm-ER alpha and Rm-ER beta cDNAs included a serine-rich region when compared to other teleost fish ER genes. Tissue-specific expression of Rm-AR and Rm-ER beta mRNAs in adult hermaphrodite R. marmoratus was high in the gonad, while Rm-ER alpha mRNA was high in the liver based on real-time RT-PCR. In addition, Rm-AR and Rm-ER alpha mRNAs increased along with developmental stage from stage 3 (5 dpf) to hatching, while Rm-ER beta mRNA increased from stage 2 (2 dpf). To uncover the effect of estrogenic chemicals on R. marmoratus, we exposed the fish to NP (300 mu g/1) and BisA (600 mu g/1) for 96 h. Significant down-regulation of Rm-AR, Rm-ERa, and Rm-ER beta mRNA was observed in gonadal tissue after exposure to NP but not BisA. In the liver, there were gender differences in gene expression after EDC exposure. These results demonstrate that expression patterns of the Rm-AR, Rm-ER alpha, and Rm-ER beta genes in the hermaphroditic fish, R. marmoratus, vary according to tissue and developmental stage as well as the specificity of environmental estrogenic chemicals. These genes can be useful as molecular biomarkers in assessing the potential impact of estrogenic compounds using this species as a model system. (c) 2006 Elsevier Inc. All rights reserved.