Possible tumour-initiating and -promoting activities of 3-diazo-N-nitrosobamethan in rat stomach mucosa.

3-Diazo-N-nitrosobamethan (DNB), a mutagen produced by nitrite treatment of bamethan, a cardiovascular drug, induced unscheduled DNA synthesis in the pyloric mucosa of the stomach of male F344 rats 2 h after its administration by gastric tube at doses of 75 to 225 mg/kg body wt. DNB at a dose of 225 mg/kg body wt induced up to a 13-fold increase in replicative DNA synthesis with a maximum at 16 h after its administration. Moreover at doses of 75 to 225 mg/kg body wt, it induced up to a 12-fold increase in ornithine decarboxylase activity with a maximum after 16 h. The present results suggest that DNB has possible tumour-initiating and -promoting activities in the pyloric mucosa of the rat stomach. However, the possible risks to patients posed by clinical use of bamethan cannot be evaluated until further work is completed.