Localization and Binding of N′-Nitrosonornicotine Metabolites in the Nasal Region and in Some Other Tissues of Sprague-Dawley Rats¹

Microautoradiography of the nasal region of the Sprague-Dawley rat after N′-[¹⁴C]nitrosonornicotine administration showed the highest labeling in the subepithelial glands (Bowman's glands) beneath the olfactory epithelium. A lower but distinct radioactivity was also present in the olfactory and respiratory epithelia, covering various parts of the nasal cavity. An exception was the vomeronasal organ, in which neither the olfactory nor the respiratory epithelium was labeled. Determination of the radioactivity bound to DNA, RNA, and proteins isolated from the nasal mucosa and the liver after N′-[¹⁴C]nitrosonornicotine administration showed a higher binding of radioactivity to protein and RNA in the nasal mucosa than in the liver, whereas the binding to DNA was somewhat higher in the liver than in the nasal mucosa. Estimations of tissue-bound and non-tissue-bound radioactivity in various tissues of rats given N′-[¹⁴C]nitrosonornicotine showed high levels of non-bound radioactivity in the preputial, submaxillary, and Zymbal's glands, whereas a considerable level of tissue-bound radioactivity was present in the nasal mucosa and the liver and also in the esophagus, trachea, and lung. Microautoradiography of the latter tissues showed that this labeling was localized to the epithelia of the esophagus, trachea, and bronchial tree, respectively.