Increase of nicotinamide methyltransferase and N1-methyl-nicotinamide oxidase activities in the livers of the rats administered alkylating agents.

Twenty four hours after intraperitoneal injection of alkylating agents, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), N-methyl-N-nitrosourea (MNU) and methyl methanesulfonate (MMS), into rats, an increase in nicotinamide (Nmd) methyltransferase and N1-methylnicotinamide (1-CH3Nmd) oxidase activities in the liver was found. Since activities of these enzymes in the liver extracts were not stimulated directly by these agents in vitro, it is postulated that the increases in these enzyme activities are due to the induction of each enzyme.