Journal of Steroid Biochemistry & Molecular Biology 123 (2011) 115–121 Contents lists available at ScienceDirect Journal of Steroid Biochemistry and Molecular Biology journal homepage: www.elsevier.com/locate/jsbmb Estrogen receptors in medaka (Oryzias latipes) and estrogenic environmental contaminants: An in vitro–in vivo correlation  Tapas Chakraborty a,b,c,d , Yoshinao Katsu c,e , Lin Yan Zhou a,b , Shinichi Miyagawa c , Yoshitaka Nagahama a,b , Taisen Iguchi c,∗ a Laboratory of Reproductive Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan b SORST, Japan Science Technology Corporation, Kawaguchi, Saitama 332-0012, Japan c Laboratory of Molecular Environmental Endocrinology, Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, Okazaki 444-8787, Japan d Division of Fish Genetics and Biotechnology, Central Institute of Fisheries Education, Mumbai 61, India e Laboratory of Reproductive and Developmental Biology, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan article info Article history: Received 23 August 2010 Received in revised form 20 November 2010 Accepted 30 November 2010 Keywords: Estrogen receptors Medaka Gonads Liver Brain Estrogenic contaminants abstract In many vertebrates, estrogens are necessary to promote the growth and differentiation of the female reproductive system during development, and have important reproductive roles in both males and females. Medaka (Oryzias latipes) has three estrogen receptor (ER) subtypes, ER˛, ERˇ1 and ERˇ2. To evaluate the three medaka ER (mER)-ligand interactions, we applied the ERE-luciferase reporter assay system to characterize each ER subtype. In this transient transfection assay system using mammalian cells, the mER proteins displayed estrogen-dependent activation. 17-Estradiol (E 2 ) and op’-DDT showed high activation irrespective of ERs. Endosulfan also exhibited activation; with less/no transactivity measured using other pesticides, i.e., heptachlor, carbendazim, deltamethrin, acephate, dimethoate and amitraz. It was generally observed that ERˇ2 had higher activation potential than ER˛ and ERˇ1. To understand the molecular mechanism of estrogen action via ER, we also conducted E 2 treatment where we observed a trigger in ERˇ2 expression upon E 2 exposure. The present data suggest that ERˇ2 is essential for female gonad maintenance. The data were supported by induction of vitellogenin (VTG) mRNA in the liver and reduced VTG receptor mRNA expression in the gonad of both sexes. The present work will provide a basic tool allowing future studies to examine the receptor–ligand interactions and endocrine disrupt- ing mechanisms, and also expands our knowledge of estrogen action on reproductive development in medaka. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction Endocrine disrupting chemicals (EDCs 1 ) and their effect on the health of wildlife and humans have recently become a major con- cern. In recent years, substantial numbers of studies have confirmed that several chemical compounds, such as agriculture runoffs, prevalent in the aquatic environment exhibit endocrine disrupting activities in fish, potentially through bioaccumulation [1,2]. There-  Grant support: Grants-in-Aid for Scientific Research from Ministry of Education, Science, Culture, Sports, Science and Technology, Japan (T.I., Y.K.) and grants from the Ministry of the Environment, Japan (T.I., Y.K), the SORST Research Project of Japan Science and Technology Corporation, and Environmental Endocrine Disruptor Studies from the Ministry of the Environment, Japan (Y.N.). ∗ Corresponding author at: Division of Molecular Environmental Endocrinology, National Institute for Basic Biology, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan. Tel.: +81 564 59 5235; fax: +81 564 59 5236. E-mail address: taisen@nibb.ac.jp (T. Iguchi). 1 Endocrine Disrupting Chemicals. fore, the endocrine disrupting effects and their intensities must be evaluated in order to confirm the safety of both preexisting and novel chemicals. Many of such chemicals show higher estrogenic potential and display potential binding to human ER˛ in the 3-D QSAR 2 (three-dimensional quantitative structure-activity relation- ship) model, with 82% accuracy [2]. Estrogen is well known for its involvement in several essen- tial phenomena, i.e. development, differentiation, reproduction and homeostasis in vertebrates. Thus, estrogenic chemicals are of par- ticular concern with regard to undesirable effects on fish [3]. Fish show abnormalities along male or female developmental path- ways exposed to sex steroid hormones and their chemical mimics, and other environmental factors (e.g. temperature), during early life, may result in functional sex changes against the genetic sex in fish [4]. Estrogen treatment, for example, leads to feminized gonads in roach (Rutilus rutilus) [5]. Studies on wild populations of 2 Three-dimensional Quantitative Structure-Activity Relationship. 0960-0760/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jsbmb.2010.11.015