Effects on circulating steroid hormones and gene expression along the hypothalamus–pituitary–gonadal axis in adult Japanese quail exposed to 17β-trenbolone across multiple generations

We investigated the effects of the androgenic growth promoter 17β-trenbolone (17βTB) on adult Japanese quail (Coturnix japonica) exposed across three generations. The F0 generation was exposed after sexual maturity to 0, 1, 5, 10, 20, and 40 ppm through feed. The F1 generation was exposed in ovo by maternal transfer and through feed at the same doses as their parents. The F2 generation was exposed in ovo only. Levels of plasma sex steroids, gonadal Cytochrome P450 aromatase (CYP19A1) mRNA and select brain neuroendocrine peptide mRNAs were measured. In males, testosterone levels did not differ in any generation from those in controls. Estradiol was significantly elevated in 17βTB treated F0 and F1 males. In F0 and F1 females, testosterone was suppressed by 17βTB, whereas estradiol was significantly higher at 40 ppm in F0 and at 10 ppm in F1 females. CYP19A1 expression in F1 males and females increased suggesting a compensatory response to the androgenic effects of 17βTB. Few significant effects were observed in the F2 birds indicating that in ovo exposure had limited effects on the monitored endpoints. Overall, our results confirmed endocrine disrupting effects of dietary 17βTB in Japanese quail but the response was dependent on sex, developmental stage at initiation of exposure, and dose.