| In oviparous vertebrates, estrogen stimulates the liver to produce vitellogenin. Vitellogenin induction is a useful biomarker for exposure to endocrine disruptors, specifically environmental estrogens. The objective of this project was to design in vivo bioassays for environmental estrogens based on induction of vitellogenin in male Xenopus laevis . Frogs were exposed to ethinyl-estradiol by injection or immersion for different times and doses, than vitellogenin induction was assessed. An ELISA was developed to measure serum vitellogenin. Additionally, a vitellogenin rt-PCR assay was developed using species-specific vitellogenin primers, to detect mRNA induction. It was established that the induction of serum vitellogenin and hepatic vitellogenin mRNA were time and dose responsive to ethinyl-estradiol. Frogs were also immersed in xenobiotic estrogens. Serum vitellogenin was not induced by the xenobiotics; however, hepatic vitellogenin mRNA was, confirming the sensitivity of this technique. These data reveal the usefulness of vitellogenin induction assays for detecting exposure to estrogenic compounds. |
