Changes in Liver Cytoplasmic RNA after Administration of 3-Methylcholanthrene

The administration of 3-methylcholanthrene to rats is accompanied by an increase in the incorporation of orotic acid- 14 C into the 45 S cytoplasmic particle in the liver. The elevation reaches a maximum at 15 hr after the injection of the polycyclic hydrocarbon and diminishes to control values by 36 hr. This effect was also observed in adrenalectomized animals, eliminating any role of the adrenal corticosteroids in the phenomenon. In addition, the turnover of 18 and 28 S ribosomal RNA in liver cytoplasm was elevated after administration of the polycyclic hydrocarbon. These results suggest that the synthesis of ribosomal constituents, in particular, ribosomal RNA, may play an important role in the "induction" phenomenon observed in liver after administration of 3-methylcholanthrene.