Evaluation of Ability of Chemicals to Bind Frog (<I>Xenopus laevis</I>) Estrogen Receptor by <I>in Vitro</I> Binding Assay

Abstract

The in vitro binding assay seems to be a useful first screening method for endocrine disrupting chemicals. Various methods have been developed and applied to the testing of chemicals. Since these assays should be applied to estrogen receptors (ER) of not only humans but also wildlife, we previously developed a standardized in vitro binding assay system for human, quail, Japanese medaka, and Xenopus laevis ERs using a competitive enzyme immunoassay. Since that was a first report on an in vitro binding assay system for Xenopus ER␣, and the capacities of chemicals to bind Xenopus ER␣ were not tested yet, we here evaluated the ability of 20 test chemicals, which were selected by the Ministry of the Environment of Japan, to bind Xenopus ER␣. Of these, 4-nonylphenol, p-octylphenol and bisphenol A had relatively high binding capacity, and these results are similar to those obtained previously in quail ER␣.