Re : Implementation of WHO Guidelines on Disclosure of Interest by members of WHO Expert Panels.

Azoxyalkanes are isomeric with nitrosodialkylamines and could be similar in their biochemical and biological actions. To compare the structure-activity relations in the two series, the tumorigenic activities of four azoxyalkanes, azoxymethane, azoxyethane, Z-ethyl-O,N,N-azoxymethane, and Z-methyl-O,N,N-azoxyethane, were compared in male F344 rats by p.o. administration of 0.54 mM and 0.135 mM solutions in drinking water. In most cases, treatment lasted 30 weeks, but at the higher dose of the two ethylazoxy compounds, 24 weeks of treatment were sufficient. Most of the animals died with tumors that could be attributed to the treatments. The two ethylazoxy compounds caused much earlier death from tumors than the corresponding methylazoxy compounds. All four compounds induced a high incidence of liver neoplasms, which were mainly hepatocellular; the two ethylazoxy compounds also induced a large number of hemangiosarcomas in the liver. At both dose levels, azoxyethane induced tumors of the esophagus and nasal cavity, tumors that were not seen in any other group. Other tumors appearing in significant incidence were in the colon and ileum, induced by azoxymethane and Z-ethyl-O,N,N-azoxymethane, and kidney tumors induced by azoxymethane and Z-methyl-O,N,N-azoxyethane. In F344 rats, azoxyethane was similar in carcinogenic activity to its isomer nitrosodiethylamine, whereas azoxymethane was much less potent than nitrosodimethylamine and induced quite different tumors. These results suggest that the biochemical activation of azoxylkanes is different from the analogous nitrosodialkylamines.

Four nitrosomethylalkylamines were given to F344 rats in drinking water at concentrations of 0.22 mM or less. The total doses delivered to each animal were 0.5 and 0.2 mmol of nitrosodimethylamine (NDMA), 0.6 mmol of nitrosomethyl-2-oxopropylamine (NMOP) and nitrosomethyl-2-hydroxy-propylamine (NMHP) and 0.9 mmol of nitrosomethyl-2,3-dihydroxypropylamine (NMDHP). NDMA induced liver neoplasms in most of the animals, including 35% with hemangiosarcomas as well as hepatocellular tumors at the higher dose, but only hepatocellular tumors at the lower dose and the latter group of rats survived longer. NMOP induced a high incidence of esophageal tumors and NMHP induced a high incidence of both esophageal and nasal cavity tumors. NMDHP was the least potent of the 4 carcinogens, and induced lung tumors, neoplastic nodules in the liver, a few esophageal tumors and a few nasal cavity tumors, but after a long induction time.

The carcinogenicity of N-nitrosomethyl-n-propylamine and five of its derivatives, including N-nitrosomethyl-n-butylamine, was compared by oral administration of the compounds to inbred F344 rats. N-Nitromethyl-n-propylamine and N-nitrosomethyl-n-butylamine given in drinking water induced tumors of the upper gastrointestinal tract, mainly carcinomas of the esophagus, and appeared to be of comparable potency. N-Nitrosomethyl(2-hydroxypropyl)amine also mainly induced esophageal carcinomas (100% incidence) and lung tumors, whereas N-nitrosomethyl(2,3-dihydroxypropyl)amine mainly induced nasal cavity tumors and gave rise to a high incidence of esophageal tumors; however, it appeared to be less potent than the monohydroxy compound. N-Nitrosomethyl(2-oxopropyl)amine, the ketone corresponding to N-nitrosomethyl(2-hydroxypropyl)amine, was a more potent carcinogen than the latter at comparable doses in drinking water and gave rise to a high incidence of esophageal tumors and tumors of the trachea; female rats had a high incidence (15/20) of angiosarcomas of the liver, but only 2 male rats died with this tumor. When N-nitrosomethyl(2-oxopropyl)amine was administered at a lower dose in drinking water or at the same dose given by gavage, the incidence of esophageal tumors was lower and there were fewer carcinomas. After administration of large doses in drinking water to male and female rats, N-nitrosomethyl(3-carboxypropyl)amine, a urinary metabolite of several N-nitrosomethyl-n-alkylamines that induce tumors of the urinary bladder in rats, gave rise to a high incidence of transitional cell carcinomas of the bladder. The time to death of animals with these tumors was long, and there were few other tumors.