Transcription profiling by array of rat testis after treatment with 17a-ethynyl estradiol, genistein or bisphenol A

The purpose of this study was to determine 1) the transcriptional program elicited by exposure to three estrogen receptor (ER) agonists: 17 a-ethynyl estradiol (EE), genistein (Ges) and bisphenol A (BPA) during fetal development of the rat testis and epididymis; and 2) whether very low dosages of estrogens (evaluated over five orders of magnitude of dosage) produce unexpected changes in gene expression (i.e., a non-monotonic dose-response curve). In three independently conducted experiments, Sprague-Dawley rats were dosed (s.c.) with 0.001-10mg EE/kg/day, 0.001-100 mg Ges/kg/day or 0.002-400mg BPA/kg/day. While morphological changes in the developing reproductive system were not observed, the gene expression profile of target tissues were modified in a dose-responsive manner. Independent dose-response analyses of the three studies identified 56 genes that are significantly modified by EE, 28 genes by Ges and 15 genes by BPA (out of 8740). Even more genes were observed to be significantly changed when only the high dose is compared with all lower doses: 141, 46 and 67 genes, respectively. Global analyses aimed at detecting genes consistently modified by all of the chemicals identified 52 genes whose expression changed in the same direction across the three chemicals. The dose-response curve for gene expression changes was monotonic for each chemical, with both the number of genes significantly changed and the magnitude of change, for each gene, decreasing with decreasing dose. Using the available annotation of the gene expression changes induced by ER-agonist, our data suggest that a variety of cellular pathways are affected by estrogen exposure. These results indicate that gene expression data are diagnostic of mode of action and, if they are evaluated in the context of traditional toxicological end-points, can be used to elucidate dose-response characteristics.

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Naciff JM, Hess KA, Overmann GJ, Torontali SM, Carr GJ, Tiesman JP, Foertsch LM, Richardson BD, Martinez JE, Daston GP