Change of mutagenic activity of N-methyl-N-nitrosoguanidine during its decomposition studied by SOS chromotest.

N-methyl-N-nitrosoguanidine (MNNG) decomposition kinetics in H2O was studied under in vitro conditions by spectrometry in different buffers and at different pH. Parallely the change of mutagenic activity of decomposing mixture was studied by SOS chromotest (in which the change of beta-galactosidase was observed). The MNNG decomposition was confirmed to be the reaction of the pseudofirst order. MNNG mutagenic activity decreases parallely with MNNG decomposition. From the observed facts it has been concluded that the MNNG decomposition proceeding outside the biological target gradually leads to the inactive stable decomposition products.