Early time-responses in estrogen regulated transcriptome in Atlantic cod (Gadus morhua) exposed to ethynylestradiol

Estrogens regulate many reproductive processes in fish and other vertebrates. Atlantic cod (G. morhua) were purchased from Havbruksstasjonen in Tromsø AS (Nofima, Tromsø, Norway) and kept in 500 L tanks in 10°C, 34 ppt seawater with a 12 h light/l2 h dark cycle at the Industrial and Aquatic Laboratory (Bergen, Norway). The fish, approximately 1.5 years old were fed with a commercial diet (Amber Neptune, Skretting, Stavanger, Norway) until the start of the treatment. In this experiment to map early time-responses in transcriptome (Experiment 2), 1.5-year-old juvenile male Atlantic cod (18 fish per group) were injected with a single dose of each of EE2 (50 nanomole/kg BW or 14.8 µg/kg BW), BPA (40 µmol/kg BW or 9.1 mg/kg BW) or MXC (40 µmol/ kg BW or 13.8 mg/kg BW) and sampled at 20 h or 48 h post injection. After dissection of each fish, a small piece pf liver tissue was sampled and snap-frozen individually in liquid nitrogen and stored at -80 °C until RNA extraction.