Differential staining of normal and neoplastic mouse lung epithelia by succinate dehydrogenase histochemistry

The cell type of origin of primary mouse lung tumors was investigated histochemically. Succinate dehydrogenase (SDH) histochemistry readily differentiated bronchiolar epithelial (Clara and ciliated) cells from alveolar type II pneumocytes in mice aged 10 days through adult. Correspondingly, freshly-isolated Clara cells stained intensely but type II cells did not. Urethane-induced papillary adenomas exhibited intense SDH staining while alveolar adenomas stained very lightly. The relative SDH activities of these two types of pulmonary adenomas is consistent with the hypothesis that alveolar tumors arise from type II pneumocytes and papillary tumors from Clara cells.