Distribution of Mutagens in Tama and Ayase River Sediments

Abstract

We measured the DNA attacking ability and the mutagenic activity of water extracts from the sediments of the Tama River and the Ayase River, two rivers flowing through heavily urban areas in Japan. The rec-assay employing recombinationless mutant of Bacillus subtilis detected DNA attacking ability in water extracts from sediments of the Tama midstream and downstream and of the Ayase midstream. The reversion assay employing the strain TA 98 of Salmonella typhimurium revealed mutagenic activity in water extracts from sediments of both the Tama and the Ayase from midstream to downstream; mutagenic activity was not detectable in the upstream sediments. Since the mutagenic activity in the majority of sampling stations grows remarkably when the metabolic action system of the rat liver is caused to work on the water extract samples, the presence of a precursor can be inferred which indicates the mutagenicity upon the work of the enzymes of the liver metabolism.By means of an assay for pH fractionation of water extracts from river sediments containing mutagens, the presence of various types of DNA attacking substances ranging from acidic compounds to neutral ones and amphoteric ones was confirmed. In addition, it was found, in terms of the gel filtration chromatography of the water extracts, that the DNA attacking chemicals are of different types in the Tama and the Ayase Rivers.