A method was developed to measure the estrogenic and antiestrogenic effects of various chemicals and organochlorine extracts in chicken embryo primary hepatocyte cultures. Messenger RNAs (mRNAs) for the estrogen-inducible egg yolk proteins, vitellogenin II (VTGII), and very low-density lipoprotein apoprotein II (apoII), were measured by multiplex quantitative reverse transcription-polymerase chain reaction (Q-PCR). After 48 h of exposure, both VTGII and apoII mRNA levels were induced by moxestrol (1-1,000 nM), 17 beta-estradiol (10-1,000 nM), o,p'-DDT (apoII: 1,000 and 10,000 nM, VTGII: 10,000 nM), 4-tertoctylphenol ([OP]; apoII: 20 and 50 microM, VTGII: 10-50 microM), and methoxychlor ([MXCL]; apoII: 5-50 microM, VTGII: 20 and 50 microM). Tamoxifen (100 and 1,000 nM) induced apoII mRNA only, and bisphenol A (BPA) was not estrogenic. Inhibition of moxestrol-mediated VTGII or apoII mRNA induction by MXCL, o,p'-DDT and tamoxifen indicated that these chemicals were also antiestrogenic at concentrations similar to those which caused estrogenic responses. Organochlorine extracts prepared from herring gull embryo yolk sacs obtained from three Great Lakes sites and one Atlantic coast site (reference site) did not show any estrogenic activities. However, the same extracts from all three Great Lakes sites had antiestrogenic activities. These results indicate that wild birds may be susceptible to the estrogenic or antiestrogenic effects of environmental contaminants.