Carcinogenesis by nitrosomorpholines, nitrosooxazolidines and nitrosoazetidine given by gavage to Syrian golden hamsters.

Five cyclic nitrosamines, four containing oxygen in the ring, were administered by gavage to groups of 20 male Syrian golden hamsters. After administration of very similar doses, nitrosomorpholine, nitroso-2-methylmorpholine and nitroso-5-methyl-1,3-oxazolidine caused the animals to die with tumors after similar times, but nitrosomorpholine induced mainly tumors of the nasal cavity (and a few of the trachea), whereas the 2-methyl derivative induced tumors of the nasal cavity and liver. While nitroso-1,3-oxazolidine and its 5-methyl derivative both induced liver tumors (but no tumors in the nasal cavity) those induced by the former compound took much longer to kill the animals. Nitrosoazetidine, a liver carcinogen in rats, but which had been reported to be inactive in hamsters, did induce tumors of the liver in 30% of hamsters after a much larger dose than the other cyclic nitrosamines.