Effect of 3-methylcholanthrene on RNA polymerase and protein kinase activities and on the nuclear ultrastructure of rat liver.

The polycyclic aromatic hydrocarbon 3-methylcholanthrene (3-MC) is a well known inducer of the microsomal mixed function oxidase enzyme system in rat liver cells. It seems probable that the inductive action of 3-MC is realized, at least partly, at the transcriptional level of protein synthesis regulation. The present experiments indicated that in the liver of young rats there was a significant alteration in the activities of nucleolar as well as nucleoplasmic protein kinase and RNA polymerase enzymes during the first days of exposure to a single dose of 3-MC. The ultrastructural investigations showed that 3-MC treatment caused nucleolar hypertrophy and accumulation of lipid inclusions in the nucleoplasm.