Figure 2.

Schematic of how steroid metabolism is altered during the first nine days of embryonic development in T. scripta when eggs are exposed to the endocrine disruptor bisphenol-A. In the control eggs, oestradiol (E₂) is converted to oestrone (E₁), and then to oestrone sulfate (E₁S) which is present at high levels in the egg. Eggs treated with BPA maintained higher levels of both E₂ and E₁, with little to no E₁S being formed. Our data indicate that BPA interferes with the metabolic conversion of E₁ to E₁S in ovo.