Diethylnitrosamine-induced hepatic tumors in wild vs. inbred strains of a viviparous fish.

A comparative study was made of the induction of hepatic tumors by diethylnitrosamine in 4 inbred strains, 3 hybrids from crosses between inbred strains, and 2 wild stocks of the viviparous fish Poeciliopsis lucida. Young fish, 1-36 days old, were administered diethylnitrosamine at concentrations of 25 ppm, 50 ppm, and 125 ppm for 3 to 5 successive 23-24-hour periods at one-week intervals. Primary neoplasms with histological characteristics of hepatocellular carcinomas were induced in fish exposed to 125 ppm of diethylnitrosamine for 3-5 successive periods at an incidence that increased from 58 percent to 93 percent directly with the number of exposures. They were not found in fish administered the lowest dose used (25 pm:3X) but a low incidence, 3-10 percent, occurred in fish receiving 3-5 exposures of the carcinogen at 50 ppm. No significant differences in tumor inducibility were found among the inbred strains, their hybrids, or the wild stocks.