|
Medakas(Oryzias latipes) were exposed continuously for 60 days to urethane at concentrations of 0, 100 and 200 ppm. After exposure, fish were placed in clean, carcinogen-free water. The medakas were sampled for pathological examination after 1 week, 2 weeks, and 1 month. Grossly visible liver tumors were not evident in all exammined fishes. However, in 5 fish from the 200 ppm group at the 2 weeks sampling period, focal areas of cellular alteration were noted in the liver. At the 1 month after exposure, 2 of 10 fish from the 100 ppm and 8 of 10 fish from the 200 ppm treatment groups displayed focal areas of highly basophilic cells in the livers. The incidence of the focal areas increased proportionately with the concentration of urethane and the age of the fish. No liver lesions or tumors were observed in controls.
|