Advanced fluorescence in situ hybridization to localize and quantify gene expression in Japanese medaka (oryzias latipes) exposed to endocrine-disrupting compounds

In an earlier study, we described the development of fluorescence in situ hybridization (FISH) using confocal microscopy to localize and quantify gene expression in fish. Here, we report the results of FISH application to investigate effects of model endocrinedisrupting chemicals (EDCs), 17α-ethinylestradiol (EE₂) and 17β-trenbolone (TB), on expressions of EDC-responsive genes in Japanese medaka (Oryzias latipes) at the cellular/tissue level paired, with histological observation. Gene expressions of vitellogenin-II (Vit-II), androgen receptor (AR), and cytochrome P450 gonadal aromatase (CYP19a) were determined after exposure to 5, 50, or 500 ng/L of EE₂ or 50, 500, or 5,000 ng/L of TB for 7 d. Exposure to the greatest concentration of EE₂ or TB significantly reduced fecundity and caused histological alterations in gonads. 17α-Ethinylestradiol induced. Vit-II expression in both male gonads and liver relative to controls and resulted in greater intensity of hematoxylin staining in hepatocytes, which was significantly correlated, with VitII induction in liver. When exposed to EE ₂ at less than 50 ng/L, CYP19α expression associated with early stage oocytes was greater than that in controls. However, at 500 ng/L, this trend was reversed. The greater Vit-II expression in testis from all EE ₂ groups, and the lesser expression of CYP19a in ovaries from the 500 ng/L group, likely is related to changes in the number of cells in which these genes are predominantly expressed rather than to an increase in expression per cell. 17β-Trenbolone significantly induced AR expression in ovaries but did not alter AR expression in female liver. It was concluded that FISH combined with histology enables advanced elucidation of molecular effects of chemicals by associating changes in gene expression with certain tissues and/or cell types and allows these changes to be related to histological effects. Copyright © 2009 SETAC.