A REVIEW OF THE HEPATIC-TUMORS RELATED TO MIXED-FUNCTION OXIDASE INDUCTION IN THE MOUSE

Mixed-function oxidase (MFO) induction in the mouse liver results in a rapid and sustained centrilobular hypertrophy associated with a hyper plastic response. In many studies, the long-term sequela of prolonged exposure is an increased incidence of lesions considered to be adenoma s. Studies have shown in aged control mice that the burden of adenomas usually consists of lesions with basophilic cytoplasic staining and a uniform population of hepatocyte nuclei. With long-term feeding of MF O inducers, there is an additional burden of lesions diagnosed as aden omas having a different histological appearance with increased eosinop hilic cytoplasm and pleomorphic nuclei. The incidence of hepatocarcino mas usually is not modified by the increased incidence of eosinophilic adenomas. Studies into the behavior of the eosinophilic lesions show that the hepatocytes approximate in their behavior to normal and not n eoplastic cells. It is suggested that these lesions should not be cons idered a carcinogenic response to the chemical.