| Summary: | Fertility and embryo survival rates are often low in eggs from thermally challenged Tasmanian Atlantic salmon, partly due to a reduction in plasma 17β-estradiol (E 2 ) levels. We used juvenile Atlantic salmon to assess whether hepatic tissue remains responsive to stimulation by E 2 at the higher temperatures sometimes encountered by Tasmanian salmon during summer. E 2 administration stimulated vitellogenin (Vtg) and estrogen receptor alpha transcription at 14°C and 22°C, although induction of Vtg occurred more rapidly at 22°C. Consequently, plasma Vtg levels increased and reached a plateau more quickly at 22°C. Zona pellucida (Zp) B and C transcription was significantly lower in E 2 -treated fish at 22°C relative to 14°C. This shows that the Vtg gene is E 2 -responsive at high temperature unlike Zp B and C genes that displayed traits of thermal inhibition. Therefore, estrogen replacement therapy in adult salmon may offset some, but not all thermal inhibition of reproductive function.
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