Detection of Retinoic Acid Receptor Agonistic Activity and Identification of Causative Compounds in Municipal Wastewater Treatment Plants in Japan

Retinoic acid (RA) receptors (RARs) are nuclear receptors whose specific natural ligands are all-trans RA (atRA) and 9-cis RA (9cRA) derived from retinoid (vitamin A) precursors [1]. Retinoic acid receptors control aspects of vision, cell differentiation, immune response, and embryonic development in vertebrates [1, 2]. By contrast, ligands of RARs are known as potential teratogens in developing vertebrate embryos. Previous studies have demonstrated that excess RAs cause a spectrum of teratogenesis in many animals, including fish [3, 4], amphibians [5-7], and mammals [8, 9].