Induction of estrogen-responsive gene transcription in the embryo, larval, juvenile and adult life stages of zebrafish as biomarkers of short-term exposure to endocrine disrupting chemicals

Real-time quantitative RT-PCR was adopted to investigate the transcription of the estrogen-responsive genes in different developmental stages of zebrafish exposed to endocrine disrupting chemicals (EDCs). The lowest observed effect concentrations (LOECs) of 17β-estradiol for inducing vtg1 transcription were 0.25, 0.5, 0.25 and ≤ 0.1 μg/L for embryo, larvae, juvenile and adult male zebrafish, respectively, while the LOECs of nonylphenol for induction of vtgs transcription were 50 μg/L in embryo and 100 μg/L in larvae and adult stages. The mRNA levels of the two vtgs were low in both the embryo and larvae stages, even at the highest 17β-estradiol or nonylphenol exposure concentrations, while the mRNA levels in liver of adult zebrafish of the two vtgs were 102 or even 104 times higher than those of the control groups at the corresponding nonylphenol or 17β-estradiol exposure concentrations. Similarity, the ERα and ERβ mRNA levels in juvenile and adult zebrafish livers were also higher. Results suggest that in the early developmental stages of zebrafish might be more sensitive (low LOECs) to the presence of EDCs such as nonylphenol, but juvenile and adult zebrafish have a more effective (high induction levels). The use of zebrafish juveniles, larvae and embryos offers an alternative stage to detect EDCs.