Comparative study on the carcinogenicity of N-nitroso-2,6-dimethylmorpholine in the European hamster.

The effect of N-nitroso-2,6-dimethylmorpholine (NDMM), a pancreatic carcinogen for the Syrian golden hamster, was examined in the European hamster (EH) for comparative reasons. The compound was administered by subcutaneous (SC) injection or intragastric gavage (IG) at a dose level corresponding to 0.1 of LD50. In terms of carcinogenicity the main target was the respiratory epithelium (nasal cavity, lung, trachea, larynx); other benign and malignant tumors originated in the liver (bile duct epithelium and endothelium) and renal pelvis (transitional epithelium). The occurrence of neoplasms seen at other sites was difficult to attribute to treatment. Reduced metabolism as found during hibernation did not change the organ distribution of neoplastic growths. Differences in the carcinogenic potency (tumor incidence and latency, affected organs and cell types) did not depend significantly on the route of administration. The data were compared to those obtained using other nitroso compounds in this species.