Carcinogenic effect of subcutaneously administered N-nitroso-2,6-dimethylmorpholine in Syrian golden hamsters.

N-Nitroso-2,6-dimethylmorpholine (DMNM) was examined in Syrian golden hamsters in a comparative study of N-N-dipropylnitrosamine (DPN) metabolites. DMNM was administered sc, and the results were compared with those of a previous study in which the compound was given intragastrically. DMNM was more toxic when administered sc, and the respiratory tract was the main target organ (with a 100% tumor incidence). With an sc administration, neoplasms occurred earlier in the hamsters than with an intragastric administration, and fewer tumors of the pancreas and biliary tract were found. However, neoplasms of the upper digestive tract and vagina were seen only with sc treatment. These studies indicated the importance of the treatment route but did not substantiate the role of common metabolites, such as DMNM, formed by beta-oxidation from DPN, with regard to induction of a given tumor type.