Similar carcinogenic effects in rats of 1-ethyl-1-nitroso-3-hydroxyethylurea and 1-hydroxyethyl-1-nitroso-3-ethylurea

The two isomeric N-nitroso derivatives of the dialkylurea, 1-ethyl-3-(2-hydroxyethyl)urea,were given by gavage to 20 male F344 rats for 30 weeks at equimolardoses. The tumorigenic responses were compared with those toa similar dose of nitrosoethylurea or nitroso-2-hydroxyethylurea.Each of the nitrosomonoalkylureas caused death from tumors morerapidly than the analogous nitrosodialkylurea. Each of the nitrosodialkylureasinduced a broader spectrum of tumors in the rats than did eithernitrosoethylurea or nitroso-2-hydroxyethylurea, including neoplasmsof the thyroid, lung, skin, colon, mesotheliomas and neoplasmsof the brain and liver in high incidence, the last two of whichwere not seen in animals given the nitrosomonoalkylureas. Onthe other hand, there were fewer tumors of the forestomach inrats given the nitrosodialkylureas than with the nitrosomo-noalkylureas.The major difference between 1-nitroso-1-eth-yl-3-hydroxyethylureaand 1-nitroso-1-hydroxyethyl-3-ethyl- urea was that the formerinduced only neoplastic nodules in the,liver of 30% of the rats,while the latter induced hepatocellular carcinomas in 55% ofthe rats; approximately half of the rats given either compoundhad brain neoplasms, which included astrocytomas, gliomas andoligoden drogliomas.