methylazoxymethanol and Liver-Neoplasms

Topics: Aflatoxins; Alkaloids; Animals; Areca; Basidiomycota; Carcinogens; Carcinogens, Environmental; Cricetinae; Cycasin; Food Contamination; Humans; Hydrolyzable Tannins; Liver Neoplasms; Methylazoxymethanol Acetate; Mice; Neoplasms, Experimental; Plants, Medicinal; Plants, Toxic; Pyrrolidines; Rats; Safrole

To determine if hyperplastic and neoplastic lesions from medaka showed similar immunoreactivity to intermediate filament antibodies as the tissues of origin, two week old medaka were exposed to 10 or 20 mg/L of methylazoxymethanol acetate for two hours and transferred to clean water for up to six months. Using a streptavidin peroxidase method, paraffin embedded Bouins fixed neoplasms were incubated with cytokeratin, vimentin, or neurofilament antibodies. Like their nonneoplastic cellular counterparts, hepatocellular carcinoma, pancreatic acinar carcinoma and mesenchymal neoplasms including hemangioma and hemangiopericytoma reacted negatively to cytokeratin antibodies. Cholangiocarcinoma, mesothelioma, and proliferative lesions containing biliary epithelial cells reacted positively to cytokeratin antibodies. All neoplasms and proliferative lesions were negative with vimentin and neurofilament antibodies. These data indicate that while some epithelial neoplasms showed cytokeratin reactivity similar to the parent tissues, additional markers are needed to identify mesenchymal tissues and neoplasms.

Topics: Adenoma, Liver Cell; Animals; Antibodies; Carcinogens; Carcinoma, Acinar Cell; Carcinoma, Hepatocellular; Cell Division; Cholangiocarcinoma; Hemangioma; Hemangiopericytoma; Hyperplasia; Immunohistochemistry; Intermediate Filaments; Keratins; Liver; Liver Neoplasms; Methylazoxymethanol Acetate; Neurofilament Proteins; Oryzias; Pancreas; Pancreatic Neoplasms; Vimentin

For small fish species to be utilized as models for carcinogenicity testing they should be capable of developing neoplasms, preferably in multiple tissues, when exposed to known carcinogens. Seven species of small fish were exposed to methylazoxymethanol acetate (MAM-Ac) and tumor development was monitored. Specimens 6-10 days old were exposed to nominal concentrations of MAM-Ac up to 100 mg 1(-1) for 2 h, then transferred to carcinogen-free water. Hepatic neoplasms developed in the Japanese medaka, guppy, sheepshead minnow, Gulf killifish, inland silverside, rivulus, and fathead minnow. Additionally, neoplasms occurred in other organs and tissues of the medaka (retina, various mesenchymal tissues, exocrine pancreas, kidney, and nervous tissue), guppy (mesenchymal tissue, exocrine pancreas, and kidney), and sheepshead minnow (choroid gland, mesenchymal tissues, and nervous tissue). All tumors were diagnosed in specimens within 1 year post-exposure. Early signs of liver tumors appeared in medaka and guppy at about 1 month post-exposure. These studies show that both medaka and guppy would be good models because they appear sensitive to carcinogens, develop tumors in multiple tissues and are easy to breed and maintain. Certain other small fish species also may prove to be good models because of habitat preferences, breeding strategies, or genetic attributes.

Topics: Animals; Cyprinidae; Eye Neoplasms; Fishes; Liver Neoplasms; Methylazoxymethanol Acetate; Neoplasms, Experimental; Species Specificity; Water Pollutants; Water Pollutants, Chemical