[Synthesis of protein, RNA and DNA and alkylation of macromolecules in the cells of sensitive and resistant strains of ascites hepatoma 22a induced by N-methyl-N-nitrosourea].

It was shown that both in vivo and in cell suspension cultures of N-methyl-N-nitrosourea (MNM)-sensitive and resistant strains of hepatoma 22a the alkylation of macromolecules by [14C]MNM and radioactivity in the acid-soluble cell fraction and ascite fluid at different time intervals after the label injection are practically the same. The synthesis of protein, RNA and DNA in the resistant strain cells is either not impaired at all or is rapidly restored after MNM injection in vivo. The mechanism of resistance is discussed in terms of cell ability to restore DNA damage and of the lack of cell sensitivity to target cell damage due to alkylation.