Biochemical, Pharmacological And Tumorigenic Studies On A Composite Of Drinking Water Carcinogens And Mutagens Utilizing Aquatic Animals For Bioassays.
Overstreet-RM; Hawkins-WE; Walker-WW
The induction of neoplasms by methylazomethanol-acetate (592621) (MAMAc) was studied in aquatic animals. Ten day old specimens of Japanese-medaka, Gulf-killifish, sheepshead-minnows, guppies, fathead-minnows, inland-silversides, and rivulus were dosed with 0 to 100 parts per million (ppm) MAMAc for 2 hours. They were then placed in carcinogen free water and examined periodically for tumor development. MAMAc induced neoplastic lesions in the livers of specimens of all species tested. About 1 month after exposure to 50ppm or more MAMAc, the livers contained extremely hypertrophied eosinophilic cells, often concurrently with biliary duct hyperplasia. This was considered to be a cytotoxic response. These changes were followed by the development of neoplastic nodules and carcinoma patterns that progressed to lesions having anaplastic and sarcomatous features. Bile duct proliferation with cyst formation and adenofibrosis often accompanied the neoplastic lesions. Undifferentiated sarcomas of the body wall were observed in guppies and in one medaka; retinal lesions were seen in medaka. The authors conclude that several species of small fish develop hepatic neoplasms when exposed to a known carcinogen. The rate of neoplastic development and the prevalence of neoplasms vary among species and appear to be dose and possibly time dependent.
Mutagenicity; Tumorigens; Biological-effects; Sarcomagenicity; Laboratory-animals; Biochemical-analysis; Physiological-measurements; Neoplastic-agents; Carcinogenesis;
Proceedings of the Third NCI/EPA/NIOSH Collaborative Workshop: Progress on Joint Environmental and Occupational Cancer Studies