Induction of zona radiata and vitellogenin genes in estradiol and nonylphenol exposed male sheepshead minnows (Cyprinodon variegatus).

Several genes normally induced by estradiol (E(2)) in female fish, those for vitellogenins (VTGs) and zona radiata proteins (ZRPs), are also inducible in males exposed to estrogenic chemicals. Male sheepshead minnows (SHM) were exposed to both E(2) and para-nonylphenol (NP), at several doses and times to determine a dose-response. Quantitative real time PCR was used to measure mRNA for VTG1, VTG2, ZRP2 and ZRP3. Both E(2) and NP elicited a dose-response increase in all of the mRNAs tested. Exposure to both chemicals resulted in VTG2 expression at about a 10-fold lower level than VTG1, and ZRP2 expression at a lower level than ZRP3.