Early changes in regenerating hamster pancreas following a single dose of N-nitrosobis (2-oxopropyl)amine (NBOP) administered at the peak of DNA synthesis.

A single dose of N-nitrosobis(2-oxopropyl)amine, a carcinogen for hamster pancreas, was administered to hamsters with regenerating pancreas 60 hours after initiation of regeneration when the maximum number of acinar cells are in S phase of the cell cycle. This led to nucleolar segregation and mitotic abnormalities from which the acinar cells quickly recovered. Two months later there was moderate pancreatic atrophy in which there were populations of acinar cells containing a variable complement of zymogen granules. In addition, there were nests of eosinophilic cells of unknown derivation which, though disposed in configurations resembling acinar cells, differed distinctly from them. They were devoid of the rich concentric lamellar arrays of ER and zymogen granules characteristic of acinar cells. In addition, differences existed in the chromatin pattern of their nuclei and the number and morphology of their mitochondria. These results suggest that NBOP induced the emergence of a new cell population with a phenotype distinctly different from any of the component cells of normal hamster pancreas.