Use of Xenopus Laevis as a Model for Investigating in Vitro and in Vivo Endocrine Disruption in Amphibians


The estrogenic activity of 17β-estradiol (E2), α-zearalenol (α-ZEA), genistein (GEN), and 4-t-octylphenol (4-t-OP) was investigated using Xenopus laevis-based assays. All test compounds competed with [3H]E2 for binding to a recombinant Xenopus estrogen receptor (xER) with the following relative affinities: E2 > α-ZEA > 4-t-OP > GEN. the ability of these compounds to induce xER-mediated reporter gene expression was then assessed in MCF-7 human breast cancer cells cotransfected with a Gal4-xERdef chimeric estrogen receptor and a Gal4-regulated luciferase reporter gene. Luciferase activity was increased 30- to 50-fold by 10 nM E2 relative to that in solvent control. Maximal reporter gene activity induced by 10 nM α-ZEA was 54% of that induced by E2; however, the activity did not increase following doses of up to 10 μM. a dose of 1 μM 4-t-OP induced 23% of the maximal reporter gene activity induced by E2, whereas 10 μM GEN induced activity to the same level as E2. a dose-dependent increase in vitellogenin (VTG) mRNA expression was observed in Xenopus treated intraperitoneally with E2 at 0.05 to 5 mg/kg/d for three consecutive days, with the maximal induction observed in the group receiving 1 mg/kg/d. the α-ZEA, GEN, and 4-t-OP also significantly induced VTG mRNA expression, although at higher doses. These results demonstrate the utility of X. laevis as an amphibian model to assess the estrogenic activity of endocrine disruptors


Biological Sciences

Library of Congress Subject Headings

Estrogen -- receptors
Gene expression

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Article - Journal

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