Effects of diethylstilbestrol and ethinylestradiol on gene transcription of very low-density apolipoprotein II in the liver of Japanese quail, Coturnix japonica.

Very low-density apolipoprotein II (apoVLDL) is one of the constituents of yolk in avian eggs. The expression of the apoVLDL gene is highly specific to the liver in mature female birds during the egg-laying period but is stimulated by exogenous estrogens in immature male birds. In the present study, we compared the effects of two estrogenic compounds, diethylstilbestrol and ethinylestradiol, on the expression of apoVLDL mRNA in the liver of Japanese quail (Coturnix japonica). Three-week-old, immature male quail were treated with a single intraperitoneal injection of the estrogenic compounds, and the level of apoVLDL mRNA in the liver was measured by gene-specific real-time polymerase chain reaction. Diethylstilbestrol and ethinylestradiol had a similar effect on the level of mRNA, increasing it in a dose-dependent manner. Next, the levels of apoVLDL mRNA in the liver of male embryos, which were developed in fertile eggs laid by quail injected with the estrogenic compounds during yolk formation, were measured. Maternal exposure to ethinylestradiol caused an increase in the mRNA in embryos, whereas exposure to diethylstilbestrol had no effect. These results point out the importance of the route of administration to the evaluation of the estrogenic effects of endocrine disruptors in oviparous species.