Abstract

Hepatic hyperplastic nodules induced in mice by long-term griseofulvin administration were examined for selected microsomal activities and responses to enzyme inducers. Despite a decrease in microsomal cytochrome P-450 in hyperplastic nodules, aminopyrine N -demethylase was at control levels. Benzopyrene hydroxylase activity was slightly lower in microsomes derived from hyperplastic nodules than in those of control liver. Reduced nicotinamide adenine dinucleotide-cytochrome b 5 reductase was at control level, but reduced nicotinamide adenine dinucleotide- and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome c reductases and the NADPH-ferricyanide reductase were increased. NADPH-supported lipid peroxidation was lower in microsomes from hyperplastic nodules than in those from control liver, whereas microsomal stearoyl coenzyme A desaturase activity was almost doubled in the nodules. NADPH-cytochrome c reductases isolated and semipurified from hyperplastic nodule and from control liver microsomes showed almost identical affinity for NADPH. Microsomal enzymes of hyperplastic nodules responded readily to phenobarbital induction, but sodium dodecyl sulfate-polyacrylamide gel electrophoresis disclosed differences in the polypeptide patterns in the molecular weight range from 47,000 to 54,000 between microsomes derived from hyperplastic nodules and control livers. 1 Supported in part by Fonds zur Förderung der wissenschaftlichen Forschung, Grant 3580. 2 To whom requests for reprints should be addressed, at Division of Gastroenterologic Pathology and Hepatopathology (Hans-Popper-Laboratory), Department of Pathology, University of Vienna School of Medicine, Spitalgasse 4, A-1090 Vienna, Austria.