[Characteristics of mutagenesis induced by nitrosomethylurea in a mammalian multilocus system in vitro].

The mutagenic effect of short- and long-term MNU exposition causing alkylation and that combined with carbamoylation, correspondingly, at the four specific gene loci of the CHO-AT3-2 Chinese hamster line was studied. The increase both in MNU mutagenic effects and in the range of induced changes resulted from intensification of carbamoylating processes. True point mutations occurred mainly on alkylation. When carbamoylation is increased, the quantity and variety of mutations change towards accumulation of the number of other genetic lesions, for example, frameshift mutations and deletions.