Neoplasia in fish can result from contamination of waters with carcinogens and promoters. Cancer in fish, therefore, is a possible indicator of cancer risk to man and serves as a guide to the need for preventive approaches involving improved means of waste disposal and environmental hygiene. Moreover, cancer in fish indicates that this important food source may be contaminated. Detection of genotoxic carcinogens to which fish are exposed can be achieved quickly and efficiently by carefully selected batteries of complementary in vitro and in vivo bioassays. One such battery consists of the Ames test, a reverse mutation assay in prokaryotic Salmonella typhimurium, and the Williams test, involving DNA repair in freshly explanted metabolically highly competent liver cells from diverse species, including humans. Determination of DNA-carcinogen adducts by varied techniques, including 32P-postlabeling, as well as DNA breakage, mammalian cell mutagenicity, chromosome aberrations, sister chromatid exchange, or cell transformation represent additional approaches, each with its own advantages and disadvantages. More research is needed on systems to apprehend neoplasm promoters, but tests to determine interruption of intercellular communications through gap junctions appear promising. Other approaches rely on measurement of enzymes such as ornithine decarboxylase and protein kinase C. Approaches to the definition of risk to fish or humans require characterization of the genotoxic or nongenotoxic properties of a chemical, relative potency data obtained in select, limited rodent bioassays, and knowledge of prevailing environmental concentrations of specific carcinogens.
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