[Nucleotide alterations of 18 S and 28 S ribosomal RNA from rat liver during carcinogenesis induced by N-nitrosomorpholine (author's transl)].

After administration of N-nitrosomorpholine (NNM) to female Wistar-rats the ribosomal RNA (18 S and 28S rRNA) of the livers contained "abnormal" dinucleotides which were resistant against treatment with alkali or with spleen phosphodiesterase. These and further observations are discussed in view of the hypothesis that during the induction of liver tumors a metabolite of NNM causes crosslinks of nucleic acid bases. The application of this hypothesis on the effects of NNM upon DNA permits to explain the additional results that have been obtained. Observations on NNM metabolism as reported in the literature are not inconsistent with this interpretation.