title: Differential developmental toxicity of naphthoic acid isomers in medaka (Oryzias latipes) embryos.
abstract: Polycyclic aromatic hydrocarbons (PAHs) are widespread persistent pollutants that readily undergo biotic and abiotic conversion to numerous transformation products in rivers, lakes and estuarine sediments. Here we characterize the developmental toxicity of four PAH transformation products each structural isomers of hydroxynaphthoic acid: 1H2NA, 2H1NA, 2H3NA, and 6H2NA. Medaka fish (Oryzias latipes) embryos and eleutheroembryos were used to determine toxicity. A 96-well micro-plate format was used to establish a robust, statistically significant platform for assessment of early life stages. Individual naphthoic acid isomers demonstrated a rank order of toxicity with 1H2NA>2H1NA>2H3NA>6H2NA being more toxic. Abnormalities of circulatory system were most pronounced including pericardial edema and tube heart. To determine if HNA isomers were AhR ligands, spatial-temporal expression and activity of CYP1A was measured via in vivo EROD assessments. qPCR measurement of CYP1A induction proved different between isomers dosed at respective concentrations affecting 50% of exposed individuals (EC50s). In vitro, all ANH isomers transactivated mouse AhR using a medaka CYP1A promoter specific reporter assay. Circulatory abnormalities followed P450 induction and response was consistent with PAH toxicity. A 96-well micro-plates proved suitable as exposure chambers and provided statistically sound evaluations as well as efficient toxicity screens. Our results demonstrate the use of medaka embryos for toxicity analysis thereby achieving REACH objectives for the reduction of adult animal testing in toxicity evaluations.
authors.affiliation: Laboratory of Molecular Aquatic Toxicology, Division of Environmental Sciences and Policy, Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708-0328, United States.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Carney
authors.forename: Kyle
authors.initials: K
authors.lastname: Erwin
authors.forename: Ron
authors.initials: R
authors.lastname: Hardman
authors.forename: Bonny
authors.initials: B
authors.lastname: Yuen
authors.forename: David C
authors.initials: DC
authors.lastname: Volz
authors.forename: David E
authors.initials: DE
authors.lastname: Hinton
authors.forename: Seth W
authors.initials: SW
authors.lastname: Kullman
mesh_terms: D000818:Animals; D002264:Carboxylic Acids / Q000633:toxicity*; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000201:enzymology; D047108:Embryonic Development / Q000187:drug effects*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D007928:Lethal Dose 50; D016014:Linear Models; D051379:Mice; D009281:Naphthalenes / Q000633:toxicity*; D009990:Oryzias / Q000196:embryology*; D018336:Receptors, Aryl Hydrocarbon / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D015533:Transcriptional Activation / Q000187:drug effects; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D002264:Carboxylic Acids; D009281:Naphthalenes; D018336:Receptors, Aryl Hydrocarbon; D014874:Water Pollutants, Chemical; C085312:1-naphthoic acid; D019363:Cytochrome P-450 CYP1A1