In vivo and in vitro screening of endocrine disrupting chemicals with estrogenic activity in Japanese quail

This review paper describes the (1) establishment of an in vitro method for screening endocrine disrupting chemicals with estrogenic activity and (2) study on effects of nonylphenol (NP) and octylphenol (OP) on mRNA expression of vitellogenin (VTG) II and very low density lipoprotein (apoVLDL) II in the liver of quail embryos. For in vitro screening, the cDNA of the ligand binding domain of quail estrogen receptor (ER) α or quail β was ligated into the gluthathione S-transferase expression vector and expressed in E. coli. The fusion protein was used for competitive enzyme immunoassay. Of the 20 compounds examined, nine and five showed binding to ER α and ER β, respectively. NP and OP showed the highest binding to ER α, and bisphenol-A to ER β, with binding affinities relative to that of diethylstilbesterol (DES; 10^-9 M) of 6% and 6.7%, respectively. For the in vivo study, quail fertile eggs were treated with a single injection of either NP or OP (10 and 100 nmole/egg, in 20 μl) on day 13 of incubation. VTGII and apoVLDLII mRNA levels on day 15 of incubation were determined by RT-PCR. A weak but distinct expression of VTG II and ApoVLDLII mRNA was observed after NP and OP, indicating that NP and OP could be endocrine disruptors in birds.