There has been considerable interest in the use of small fish models for detecting potential
environmental carcinogens. In this study, both guppies (Poecilia reticulata) and medaka (Oryzias latipes) were exposed in the aquaria water to three known rodent
carcinogens for up to 16 months.
Nitromethane, which caused mammary gland
tumors by inhalation exposure in female rats, harderian gland and lung
tumors in male and female mice, and liver
tumors in female mice by inhalation, failed to increase
tumors in either guppies or medaka. Propanediol, which when given in the feed was a multisite
carcinogen in both sexes of rats and mice, caused increased liver
tumors in male guppies and male medaka. There was reduced survival in female guppies and no increased
tumors in female medaka.
1,2,3-Trichloropropane, which when administered by oral gavage was a multisite
carcinogen in both sexes of rats and mice, caused an increased incidence of
tumors in the liver of both male and female guppies and medaka and in the gallbladder of male and female medaka. The results of this study demonstrate that for these three chemicals, under these specific exposure conditions, the fish appear less sensitive and have a narrower spectrum of tissues affected than rodents. These results suggest that fish models are of limited utility in screening unknown chemicals for potential carcinogenicity.