Sex- and tissue-specific effects of waterborne estrogen on estrogen receptor subtypes and E2-mediated gene expression in the reproductive axis of goldfish

This research examined the gene expression profile of three goldfish estrogen receptor (ER) subtypes in multiple tissues in relation to mRNA levels of aromatase B and vitellogenin (VTG) following waterborne estrogen exposures. The protocol consisted of: i) adult male goldfish in late gonadal recrudescence exposed to 1 nM 17β-estradiol (E2); ii) adult male and female goldfish in early sexual regression exposed to 1 nM E2 for 3, 6, 12 and 24 h; and, iii) sexually mature, adult male goldfish exposed to 0.3 nM 17α-ethynylestradiol (EE2) for 24 h. Liver produced the most consistent response with up-regulation of ERα in sexually regressed, mature and recrudescing males and in sexually regressed females. The dose and length of exposure, reproductive state and sex affected the auto-regulation of ERβ1 by E2. ERβ2 was not affected in any experiments suggesting it may not be auto-regulated by E2. Aromatase B and VTG gene expression were affected by E2, but also by other experimental conditions. EE2 induced liver ERα and VTG mRNA levels indicating that high environmental EE2 levels induce E2-mediated gene expression in a model teleost. These studies reveal a more complicated action of estrogenic compounds that has important implications on estrogenic endocrine disruptors in teleosts.