Affinity of [14C]nitrosopiperidine and metabolites for mouse epithelial tissues

Male C57BL/6J mice were each administered iv 1.2 mg/kg (6.0 to 7.6 muCi) of [14C]nitrosopiperidine ([14C]NPIP) and frozen by immersion in dry ice/hexane at 0.1, 0.33, 1, 3, 9, and 24 hr after injection. The mice were processed for whole-body autoradiography without thawing or the use of any solvents; sagittal sections of the frozen mice were freeze-dried and placed on X-ray film to reveal areas of localization of radioactivity. The autoradiographs revealed intense localization of radioactivity at 6 min in the epithelium of the nose and bronchi, as well as in the liver, kidney, and salivary glands. There is virtually no affinity of [14C]NPIP for melanin. Most of the same localizations persisted from 6 min through 24 hr. At 24 hr the most intense accumulation was in the epithelium of the bronchi, nose, salivary gland ducts, and esophagus as well as the liver and Harder's gland. The results are interpreted to suggest that at least one metabolite of NPIP which localizes in the sites where tumors occur may be similar to a metabolite of NNN. The distribution is consistent with metabolic conversion of [14C]NPIP in liver and epithelium of nose and bronchi with subsequent localization of the metabolite in epithelium of esophagus and salivary gland ducts.