抄録
The Salmonella/microsome assay (Ames test) is a useful method for screening mutagens in complex environmental mixtures such as river water and sediment. However, no quantitative and generalized method to evaluate mutagenicity of complex mixtures like sediment has yet been established. In this study, the relationships between coexisting substances and the optimum amounts of S9 were investigated for the Ames mutagenicity tests of complex sediment extract. The strain Salmonella typhimurium TA98 was used.
o-Phenylphenol (o-PP) and di-2-ethylhexyl phthalate (DEHP), which are commonly found in an aquatic environment, and two kinds of sediment extract were used as model coexisting substances. The sediment extract was prepared by extracting with dichloromethane/ethylalchol (4: 1) and refining with reduced-Cu column. The mixtures of these coexisting substances and a fixed amount of the standard mutagens, 3-amino-l-methyl-5H-pyrido [4,3-b] indole (Trp-P -22) or 2-aminofluorenc (2-AF), were tested in changing amounts of S9.
Consequently, it was found that the coexistence of o-PP and the sediment extracts shifted the optimum S9 amounts of the standard mutagens and much influence on the results of the mutagenicity test. On addition of 20μl of S9, o-PP and sediment extracts gave the toxic influence on the TA98 strain, and was more inhibitory in greater amounts. On addition of 50μl, the mutagenicity decreased in the coexistence of over 200μg of the sediment extract, though 2 -AF showed high mutagenicity in the coexistence of c.a. 100μg. It was suggested that the influence was associated with the reactions between S9 and coexisting substance, especialy midium polar substances.
