Carcinogenesis in Fish Livers: Is Pollution a Factor?

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M.S. Marine Biology

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Reports of neoplasms in ectothermic animals began appearing in the literature as early as the last half of the 19th century, and by the 1900's tumors ·had been described in bivalve mollusks and bony fish (Harshbarger and Clark, 1990). J.C. Harshbarger compiled a list of tumors found in animals from 1965-1989 called the Registry of Tumors in Lower Animals (RTLA). Over the past 25 years there have been increasing numbers of fish tumors recognized (Harshbarger and Clark, 1990). Historically, the initial discovery of epizootic liver neoplasms in fish occurred in 1964 after the onset of the exponential growth of industries producing synthetic organic chemicals which began about 1940 (Harshbarger and Clark, 1990).

Chemical contaminants have been implicated in the formation and cause of tumors in fish populations that inhabit freshwater and esturine ecosystems receiving industrial and urban pollution (Metcalf et al., 1990). Polycyclic aromatic hydrocarbons (PAH's) are almost certainly involved in the development of tumors in fish populations, with liver tumors being the specific neoplasms most closely associated with a chemical etiology (Metcalf et al ., 1990).

It is generally believed that the initiating event for chemical carcinogenesis is covalent binding of chemicals and their metabolites to DNA, resulting in the formation of carcinogen DNA adducts (Maccubbin et al., 1990). It is believed that DNA lesions can occur prior to tumor formation which is consistent with the concept that the lesions could be linked to tumorigenesis (Matins and Haimanot, 1991 ).

The objective of this paper is to review the most recent data on the role of chemical contaminants in the development of tumors in fish and the possible mechanisms of tumor development.

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