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Developmental toxicity of p,p′ ‐dichlorodiphenyltrichloroethane, 2,4,6‐trinitrotoluene, their metabolites, and benzo[ a ]pyrene in Xenopus laevis embryos
Author(s) -
Saka Masahiro
Publication year - 2004
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/03-272
Subject(s) - ec50 , toxicity , developmental toxicity , teratology , xenopus , trinitrotoluene , benzo(a)pyrene , pyrene , toxicology , ecotoxicology , oryzias , chemistry , tributyltin , biology , pharmacology , environmental chemistry , biochemistry , in vitro , fetus , pregnancy , organic chemistry , gene , genetics , explosive material
Since 1995, high incidences of deformed frogs have been documented in Kitakyushu, Japan. In this area, relatively high concentrations of DDT, trinitrotoluene (TNT), their metabolites ( p,p ′‐dichlorodiphenyldichloroethylene [DDE], p,p ′‐dichlorodiphenyldichloroethane [DDD], 2‐amino‐4,6‐dinitrotoluene [2ADNT], and 4‐amino‐2,6‐dinitrotoluene [4ADNT]), and benzo[ a ]pyrene [B a P]) have been identified from field samples. I used a standardized assay with Xenopus laevis embryos (frog embryo teratogenesis assay— Xenopus , FETAX) to examine the developmental toxicity of these compounds. Both DDE and B a P were considered nearly nontoxic in embryonic development because they induced low (<10%) mortality and malformation incidence even at the highest concentrations tested (DDE, 393 μM; B a P, 13.2 μM). The DDD (96‐h median lethal concentration [LC50] = 44.1 μM, 96‐h median effective concentration [EC50] for malformation = 14.9 μM) was more lethal and teratogenic than its parent compound, DDT (96‐h LC50 = 101 μM, 96‐h EC50 = 41.5 μM). Predominant symptoms observed were axial malformations (DDT and DDD) and irregular gut coiling (DDT). However, DDT and DDD should not act as major lethal or teratogenic toxicants in the aquatic environment within a short‐term exposure via water because their 96‐h LC50 and 96‐h EC50 values were extremely high, considering their low solubility in water. The TNT (96‐h LC50 = 16.7 μM) was more lethal than 2ADNT (96‐h LC50 = 166 μM) or 4ADNT (96‐h LC50 = 115 μM). Although 4ADNT (96‐h EC50 = 85.8 μM) induced various tadpole malformations, it was a weak teratogen compared with TNT (96‐h EC50 = 9.78 μM) and 2ADNT (96‐h EC50 = 16.9 μM). The most typical malformations observed were axial malformations, eye abnormalities (TNT), edema, and irregular gut coiling (2ADNT and 4ADNT). The 96‐h LC50 and 96‐h EC50 values of TNT, 2ADNT, and 4ADNT were lower than their saturated concentrations in water. Therefore, these nitroaromatic compounds may show lethal or teratogenic effects on aquatic animals if their habitats are severely contaminated with TNT.