Pathology of diethylnitrosamine toxicity in the fish Rivulus marmoratus.

Rivulus marmoratus were exposed to 0, 10, 21, 45, 95, or 200 mg/liter diethylnitrosamine (DEN) for 6 weeks and examined 12 weeks after the end of exposure. Fatty change, hepatocellular glycogenosis, multiple basophilic foci, enlarged and distorted cells with or without an enlarged nucleus, and hyaline bodies and cytological alterations observed after exposure to DEN. Hemangiomas, cholangiomas, biliary cystadenomas, and glandular, trabecular and anaplastic hepatocellular carcinomas were observed at the 18th week. Only those fish exposed to 95 mg/liter DEN had cavernous hemangiomas and peliosis-like lesions, which could be a preneoplastic lesion preceding cavernous hemangiomas. Adenomatous hyperplasia of thyroid and granulomas were other chronic reactions caused by DEN toxicosis.