Effects of endocrine disrupting chemicals on the expression of CYP19 genes in zebrafish (Danio rerio) juveniles.

Cytochrome P450 aromatase (CYP19) is the key steroidogenic enzyme responsible for conversion of androgens to estrogens which play a critical role in developmental sex differentiation and adult reproductive cycles in vertebrates. To evaluate the potential roles of endocrine disrupting chemicals (EDC) on reproductive physiology of fish, the influence of multiple classes of EDC on the transcript abundance of two CYP19 isoforms, CYP19A1 and A2, were investigated in zebrafish juveniles. The pharmaceutical, clofibrate, and the pesticide, atrazine, did not influence the expression of either CYP19 gene. Estrogenic compounds, nonylphenol (NP) and a pharmaceutical estrogen, ethinylestradiol (EE), strongly enhanced the expression of CYP19A2 gene in dose-dependent manner. Exposure to benzo[a]pyrene (BaP) significantly increased CYP19A2 transcript abundance. Furthermore, BaP when co-treated with EE partially suppressed EE-induced upregulation of CYP19A2. In contrast, the expression of CYP19A1 was basically resistant to EDC treatment although EE at high concentration (1-100 nM) downregulated its expression. These findings suggest that multiple classes of EDC may potentially perturb developmental and reproductive physiology in fish through differential transcriptional modulation of the CYP19 genes with the most evident disruption in neural tissue. Copyright 2004 Elsevier B.V.