Pancreatic carcinoma induced by N-methyl-N'-nitrosourea in aged mice.

We have studied the ability of N-methyl-N'-nitrosourea to induce pancreatic carcinoma within 5 months when single doses were administered to C57BL/6J male mice at 3, 12 and 24 months of age. Pancreatic tumors were not observed in the young and middle-aged animals, but 3/15 of the surviving aged mice showed gross evidence of carcinoma. Ultrastructural analysis revealed in each tumor the presence of two populations of undifferentiated cells, both cell types possibly being of acinar cell origin. The observation of pancreatic carcinoma only in aged animals treated with an environmental carcinogen may be a model paralleling the human condition, which also shows a strong age dependency.