title: Identification of retinoic acid receptor agonists in sewage treatment plants.
abstract: Retinoic acid receptor (RAR) agonists are speculated to be one possible cause for the widely observed frog deformities in North America, although little is known about the specific RAR agonists in aquatic environments. We identified the specific RAR egonists in sewage treatment plants (STPs) and receiving rivers using an RAR yeast two-hybrid bioassay. Water samples were extracted by solid-phase extract cartridges, which were successively eluted by hexane, ethyl acetate, and methanol for bioassay. Among the three fractions, the ethyl acetate fraction showed the highest RAR agonistic activities. The bioassay-derived activity, expressed as all-trans-retinoic acid (all-transRA) equivalents (ATRA-EQ) were 10.9 +/- 2.2 and 1.7 +/- 1.0 ng/L in the STP influents and effluents, respectively, while the ATRA-EQs were as high as 7.1 and 8.3 ng/L in the two rivers receiving STP effluents. Following a two-step fractionation using high-performance liquid chromatography and ultra-performance liquid chromatography (UPLC) directed by the bioassay, two bioactive fractions were obtained from Gaobeidian STP influent and all-trans-4-oxo-RA (4.7-10.4 ng/L in influents, < 0.2-0.9 ng/L in effluents) and 13-cis-4-oxo-RA (2.3-7.1 ng/L in influents, < 0.4-1.1 ng/L in effluents) were identified in these fractions with UPLC-MS/MS. The EC50 for all-trans-4-oxo-RA or 13-cis-4-oxo-RA relative to that of all-trans-RA in exhibiting RARalpha agonistic activity was calculated to be 3.87 and 0.46, respectively.
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
authors.forename: Huajun
authors.initials: H
authors.lastname: Zhen
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Wu
authors.forename: Jianying
authors.initials: J
authors.lastname: Hu
authors.forename: Yang
authors.initials: Y
authors.lastname: Xiao
authors.forename: Min
authors.initials: M
authors.lastname: Yang
authors.forename: Junji
authors.initials: J
authors.lastname: Hirotsuji
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Nishikawa
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nakanishi
authors.forename: Michihiko
authors.initials: M
authors.lastname: Ike
mesh_terms: D002681:China; D002851:Chromatography, High Pressure Liquid; D004784:Environmental Monitoring; D018168:Receptors, Retinoic Acid / Q000819:agonists*; D045483:Rivers / Q000737:chemistry; D012722:Sewage / Q000737:chemistry*; D052616:Solid Phase Extraction; D020798:Two-Hybrid System Techniques; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification
chemical_list: D018168:Receptors, Retinoic Acid; D012722:Sewage; D014874:Water Pollutants, Chemical