EC₅₀ and LC₅₀ of Daphnia magna of acute toxicity tests for ten chemical substances (anesthetic) were determined. We also investigated the toxicity changes when the chemical substance coexists with a surfactant. The results of the binary acute toxicity tests using Daphnia magna on ten chemical substances and two surfactants, Polyoxyethylene (10) octylphenyl ether (POE) and Sodium dodecylbenzenesulfonate (DBS) were investigated using the toxic unit concept. In the case of POE-chemical system, 4 chemical substances exhibited simple additive. The other 6 chemical substances are considered to be slightly less than additive. In the case of DBS-chemical system, 7 out of 8 chemical substances tested were judged to be less than additive or antagonistic. DBS and Bisphenol A intake by Daphnia were analyzed. The decrease in the toxicity of Bisphenol A in the presence of DBS is concluded to be a decrease in the uptake of Bisphenol A in the bodies of Daphnia.

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Exposure of animals to dioxin or similar environmental pollutants evokes responses by some drug-inducible genes that are measurable in the transcriptional level for using in the early detection system. Dioxin responsive elements (DREs) located in the 5' upstream regions of the CYP1A genes of fish and other animals play a key role in the drug-inducible genes expression. Of the two CYP1A genes reported in Japanese eel, several DREs are found to exist in the 5' upstream region of the CYP1A1 (MC1) gene. However, no DREs was found within the 1631 bp upstream region of the second form of CYP1A1 (MC2) gene in a λ phage clone. In order to sequence further beyond the 1.6 kbp upstream region of the MC2 gene, a cosmid library was constructed with longer genomic fragments. We succeeded in obtaining a clone which contained both the MC1 and the MC2 genes including the further upstream region of the MC2 gene. Sequence analysis revealed that the clone contained, in addition to the 1.6 kbp region, a 3295 bp further upstream region containing eleven DREs. In MC1 as well as mammalian CYP1A1 genes, the functional DREs are found in the proximity of transcription start site, whereas the DREs of the MC2 gene were localized beyond the 1.7 kbp upstream region, which contains unusual TAA repeats.

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Assuming that fish in the wild take up polycyclic aromatic hydrocarbons (PAHs) through the food web, the juvenile flounders (Paralichthys olivaceus) were orally exposed to 400 mg/kg of crude oil from the United Arab Emirates or heavy fuel oil from the tanker Nakhodka through food contaminated with these oils. The changes in concentrations of PAHs in liver and of their metabolites in bile were studied in the during a 14-day exposure period followed by a 12-day elimination period. Total PAH concentrations in liver were 83.9 ng/g for crude oil and 71.6 ng/g for heavy fuel oil, and phenanthrene was the component with the highest concentration in each group (38.5 ng/g for crude oil and 28.9 ng/g for heavy fuel oil) after 14 days of exposure. PAHs with molecular weight greater than those of 1,2-benzanthracene and chrysene were rarely detected in liver. The PAH metabolites detected in the bile were o-, m-, and p-hydroxybiphenyls, 9-hydroxyfluorene, 9-hydroxyphenanthrene, and 1-hydroxypyrene. However, their concentrations were relatively low and roughly similar to those of PAHs in liver. On the basis of our results, we suggest that orally adsorbed PAHs do not contribute to the accumulations of PAHs and their metabolites in flounder.

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Ethyl p-hydroxybenzoate (EPH) is one of preservatives (parabens). Medaka (Oryzias latipes), about 1 year old in age, were exposed to aqueous solution of EPH at concentration of 5 ppm for 30 weeks. Histopathological examination revealed induction of vitellogenesis in either sex after 6 weeks and development of testis-ova in 3 males at the 30 weeks. These attentions are the estrogen-like activity. In addition, in female after 30 weeks, ovary-spermia was observed in ovary. This attention is the androgen-like activity. These results suggested that EPH is an endocrine disruptor on androgenesis as well as estrogenesis.

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