Hepatic transcriptomic and metabolomic responses in the Stickleback (Gasterosteus aculeatus) exposed to ethinyl-estradiol

An established three-spined stickleback (Gasterosteus aculeatus) cDNA array was expanded to 14,496 probes with the addition of hepatic clones derived from subtractive and normalized libraries from control males and males exposed to model toxicants. Microarrays and one-dimensional 1H nuclear magnetic resonance (NMR) spectroscopy, together with individual protein and gene biomarkers were employed to investigate the hepatic responses of the stickleback to ethinyl-estradiol (EE2) exposure. Male fish were exposed via the water to EE2, including environmentally relevant concentrations (0.1–100 ng/l) for 4 days, and hepatic transcript and metabolite profiles, kidney spiggin protein and serum vitellogenin concentrations were determined in comparison to controls. EE2 exposure did not significantly affect spiggin concentration but significantly induced serum vitellogenin protein at the threshold concentration of 32 ng/l. 1H NMR coupled with robust univariate testing revealed only limited changes, but these did support the predicted modulation of the amino acid profile by transcriptomics. Transcriptional induction was found for hepatic vitellogenins and choriogenins as expected, together with a range of other EE2-responsive genes. Choriogenins showed the more sensitive responses with statistically significant induction at 10 ng/l. Real-time polymerase chain reaction (PCR) confirmed transcriptional induction of these genes. Phosvitinless vitellogenin C transcripts were highly expressed and represent a major form of the egg yolk precursors, and this is in contrast to other fish species where it is a minor component of vitellogenic transcripts. Differences in inducibility between the vitellogenins and choriogenins appear to be in accordance with the sequential formation of chorion and yolk during oogenesis in fish.