Electron microscopic autoradiography of the pancreas in the hamster treated with tritiated N-nitroso-2,6-dimethylmorpholine

Syrian golden hamsters were given a single dose of [3H]-N-nitroso-2,6-dimethylmorpholine and killed 8 hr later. The pancreas was processed for electron microscopic autoradiography to detect binding of radioactivity to cellular constituents. The pancreatic acinar cells and duct epithelia were found to be labeled, while islet cells, centroacinar cells, and all nonepithelial elements were not. Acinar cells active in secreting zymogen had a high concentration of grains over the zymogen granules and the rough endoplasmic reticulum. Their nonsecreting counterparts contained abundant bound material in the nuclei and rough endoplasmic reticulum. Labeling was lower in the duct epithelia than in acinar cells, with the majority of grains associated with the heterochromatin. Our findings suggest that the acinar cells are the principle site of metabolic activation in this organ.