  The aim of this study was to identify a signal that could be used as an
androgen exposure indicator in the European bullhead (Cottus sp.). For this
purpose, the ultra-structure of the kidney was characterized to identify normal
structure of this organ, and histological changes previously described in the
kidney of breeding male bullheads were quantified using the kidney epithelium
height (KEH) assay previously developed and validated for the stickleback. In
the next step, the effect of trenbolone acetate (TbA), a model androgen, was
assessed to identify potential androgenic regulation of bullhead kidney
hypertrophy. Measurement of KEH performed on adult non-breeding male and female
bullheads exposed for 14 and 21 days to 0, 1.26 and 6.50 mu g/L showed that
kidney hypertrophy is induced in a dose-dependent manner, confirming the
hypothesis that the European bullhead possesses a potential biomarker of
androgen exposure. Combined with the wide distribution of the European bullhead
in European countries and the potential of this fish species for environmental
toxicology studies in field and laboratory conditions, the hypothesis of a
potential biomarker of androgen exposure offers interesting perspectives for
the use of the bullhead as a relevant sentinel fish species in monitoring
studies. Inducibility was observed with high exposure concentrations of TbA.
Further studies are needed to identify molecular signals that could be more
sensitive than KEH
