Multiple Responses in Gene Expression in Fish Treated with Estrogen

During the last decade there has been a significant body of research conducted on environmental estrogens. These include industrial, agricultural and pest-control chemicals that bind to the estrogen receptor and induce biological changes during development or reproduction. Most of these changes are probably due to modified gene expression, since estrogen receptors function at this level. We have mapped qualitative gene expression responses (by differential display reverse transcriptase polymerase chain reaction, DD) in adult male sheepshead minnows (Cyprinidon variegatus) receiving high dose injections (5 mg/kg), or constant flow-through aquatic exposures to environmentally relevant concentrations (100 ng/l) of estradiol-17beta, and found them nearly identical. We have observed both up-regulation and down-regulation of transcripts, which fit into known responses to estradiol. Among the genes up-regulated are vitellogenin and several vitelline envelope proteins indicating that genes for proteins involved in egg development and maturation are susceptible to environmental estrogen exposure. While physiological changes caused by estradiol treatment are not totally explained by changes at the mRNA level, those changes can nevertheless be used as fingerprints to characterize an in vivo estrogenic response.