PERSISTENCE OF METHYLATED BASES IN RIBONUCLEIC-ACID OF SYRIAN GOLDEN-HAMSTER LIVER AFTER ADMINISTRATION OF DIMETHYLNITROSAMINE

Syrian golden hamster liver ribosomal RNA was isolated up to 96 h after administration of [14C]dimethylnitrosamine at 25 mg/kg or 2.5 mg/kg body weight. The chemical alkylation products, 7-methylguanine, 3-methylcytosine, O6-methylguanosine and 1-methyladenosine, were measured after acidic or enzymic hydrolysis of the RNA to bases or mononucleosides followed by ion-exchange chromatography. Between 7 and 96 h, the relative amounts of alkylation products did not change with time even though the absolute amounts fell by approx. 80% and 51% after the high and low doses respectively. The results suggest that base specific excision repair does not exist for RNA alkylation products in this experimental system.