Estrogenic effect of the phytoestrogen biochanin A in zebrafish, Danio rerio, and brown trout, Salmo trutta

• The estrogenic effect of waterborne biochanin A was investigated in zebrafish and juvenile brown trout.
• Vitellogenin synthesis was induced after 8–10 d exposure to 10 μg biochanin A L−1 in juvenile brown trout.
• NOEC for induction of vitellogenin production in adult male zebrafish was in the range 70 and 114 μg biochanin A L−1.
• Exposure to 209 μg biochanin A L−1 60 days from hatch skewed the sex ratio toward more phenotypic female zebrafish.
• Concerning vitellogenin induction, short term tests may show a higher sensitivity than partial life cycle tests.

Isoflavones with estrogenic activity produced in Fabaceae plants are known to leach from agricultural areas to freshwater systems, but the effect of waterborne isoflavones in fish has not been thoroughly characterized. Therefore, the estrogenic effect of waterborne biochanin A was investigated in zebrafish (Danio rerio) and juvenile brown trout (Salmo trutta). Exposure of juvenile brown trout to 10 μg biochanin A L−1 or higher caused marked vitellogenin induction after 9–10 days of exposure and so did exposure to 186 μg biochanin A L−1 for 6 h. Following 8 d of exposure, a NOEC for induction of vitellogenin production in male zebrafish was 70 and LOEC 114 μg biochanin A L−1. Exposure to 209 μg biochanin A L−1 from hatch to 60 days post hatch (dph) caused a skewing of the sex ratio toward more phenotypic female zebrafish, but did not cause induction of vitellogenin in male and undifferentiated fish. In conclusion: (1) biochanin A elicits estrogenic effects in trout at environmentally realistic concentrations, (2) brown trout plasma vitellogenin concentrations respond to lower biochanin A exposure concentrations than vitellogenin concentrations in zebrafish homogenates and (3) concerning vitellogenin induction, the hypothesis should be tested if short term tests with zebrafish may show a higher sensitivity than partial life cycle tests.