魚類のPCP吸収機構の溶媒--水系分配モデルによる解析〔英文〕

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A study has been made of the absorption mechanism of pentachlorophenol (PCP) from media in goldfish, Carassius auratus, through examination of the relationship between the bioconcentration of PCP by the fish and the distribution of PCP in organic solvents/water partitioning systems at various pHs. The linear relationship was observed between the bioconcentration ratio of PCP in goldfish at 1-h exposure to 0.1 ppm PCP and the distribution ratio of PCP in both the systems of 1-octanol/water and 1-heptanol/water in the pH range from 5.5 to 10, but not in nonpolar solvents/water systems, such as xylene, n-hexane and n-heptane. The pH-dependent linear relationship between the bioconcentration ratio in the fish and the distribution ratio in the alcohol/water system demonstrates that the transfer of PCP from media to the fish is caused mainly by passive diffusion of the unionized form probably through the gill membrane. The reduction of the toxicity of PCP to the fish with an increase of the pH of media is attributed to the decrease of the concentration of the unionized PCP in the media by conversion into the ionized form, although the ionized PCP is slightly transferred to the fish presumably by hydrogenbonding with polar lipids which constitute the gill membrane.