Amitrole: strain differences in morphological response of the liver following subchronic administration to mice.

Strain differences in the induction of hepatocellular preneoplastic lesions by amitrole were examined in NOD, ICR and DS mice. Amitrole was administered to mice in drinking water at a dose of 1% for 6 months. After 3 months, hyperplastic nodules (HN) and severe fibrosis were prominent in NOD mice but not in other strains. On examination at 6 months, both number and size of HN were greatest in the NOD strain. Furthermore, a hepatocellular carcinoma was found in a NOD mouse, suggesting that this strain is more susceptible to amitrole-induced hepatocarcinogenesis than are ICR or DS mice.