Preferential inhibition of the synthesis of 45S ribosomal rna precursor by N-acetoxyacetylaminofluorene in rat liver epithelial cultures.

After exposing a line of rat liver epithelial cells to a single dose of the carcinogen N-acetoxy-2-acetylaminofluorene (N-acetoxy-AAF), a dose-dependent decrease in (3H) uridine incorporation into total cellular RNA was found. Approx. 50% inhibition occurred with 0.5 mug/ml of the compound. The kinetics of the response, the effects of actinomycin D, and the fractionation of the newly synthesized RNA by polyacrylamide gel electrophoresis indicated preferential inhibition of the synthesis of 45S ribosomal RNA precursor and relative sparing of the synthesis of heterogeneous nuclear RNA.