Deposition and clearance of labeled cigarette smoke particles in rat respiratory and digestive tract.

In this investigation 160 8-wk-old Sprague-Dawley rats inhaled smoke from 14C-labeled cigarettes in a Hamburg II smoking machine. The research cigarettes were labeled with [16,17-14C]dotriacontane. Eighty of the rats were acclimatized to smoke from nonlabeled research cigarettes for 21 d before inhaling labeled cigarette smoke. The investigation was divided into four experiments. In experiment I all rats were killed immediately after exposure to the 14C-labeled smoke from 30 cigarettes (10 muCi per cigarette) and the organs of the respiratory and digestive tracts were measured for 14C activity. These animals showed high activity in the apex nasi, fundus nasi, and larynx. The highest activity was found in the lobus dexter caudalis and the lobus sinister of the lung. The lungs contained four-fifths of the condensate inhaled into the respiratory tract. In experiment II three animals were killed immediately after smoking, three after 6 h, and four after 24 h. No activity was found after 6 h in apex, fundus nasi, larynx, and trachea. The lungs showed no clearance at all. The activity in the digestive tract was highest in the stomach and the esophagus immediately after cessation of smoking. These values decreased rapidly after 6 h. In experiment III the animals were killed after 7, 21, and 42 d. Clearance from the upper respiratory tract was fast, whereas clearance from the lungs was slow. Clearance from all lung lobes was faster in the nonacclimatized animals. In experiment IV the rats inhaled the smoke from 14C-labeled cigarettes (2 muCi per cigarette) on 5 successive days. The animals were killed 7, 14, and 21 d after the last smoke inhalation. Clearance from the lungs was slower in acclimatized and non-acclimatized animals than in experiment III.