N-nitrosodiethylamine-induced hepatocarcinogenesis in estuarine sheepshead minnow (Cyprinodon variegatus): neoplasms and related lesions compared with mammalian lesions.

Groups of estuarine sheepshead minnows (Cyprinodon variegatus) were exposed to approximately 57 mg N-nitrosodiethylamine [(DENA) CAS: 55-18-5]/liter for 5-6 weeks. Exposure was stopped and the fish were then transferred to clean, flowing seawater. Induced liver lesions were studied in periodic samples of fish taken during the next 140 weeks of holding. Lesions found following exposure were early altered basophilic and eosinophilic foci, oval cell hyperplasia, clear cell foci, neoplastic nodules, hepatocellular carcinomas, cholangiolar carcinomas, possible pericytomas originating in liver, hemangiopericytomas, spongiosis hepatis, and cholangiofibrosis. The relative prevalence of these lesions was given. Most of these lesions morphologically were compared to their counterpart lesions in the rat. Certain lesions in our fish such as hepatocellular carcinomas, cholangiolar carcinomas, pericytomas, hemangiopericytomas, spongiosis hepatis, and cholangiofibrosis have apparent similar cellular origins and morphogenesis to those lesions in rats and perhaps in other mammals. Spongiosis hepatis in the sheepshead minnow apparently arises from perisinusoidal cells and may be a neoplasm of this cell type. The general similarity of response to DENA in sheepshead minnows and rats suggests that this fish has promise as a model subject for studying some hepatocarcinogens and as a sentinel organism for detecting hepatocarcinogens in contaminated coastal waters.