Pulmonary macrophage mobilization in hamsters after cessation of smoking

Male Syrian hamsters were exposed to smoke from three different types of cigarettes rated as mild, medium, and strong on the basis of their smoke chemistry for 4 weeks. These hamsters were euthanized at 0, 1 and 2 weeks of recovery after the last smoke exposure to study the pulmonary cell response after cessation of smoking. The free macrophage count determined on lung sections stained with hematoxylin and eosin was used as the index to evaluate the rate of recovery from smoke-related insult caused by the different types of cigarettes. The number of macrophages in the smoke-exposed hamsters was consistently greater throughout the recovery period than in the controls, depending on the amount of particulate components including tar and nicotine in the test cigarettes. The macrophage mobilization peaked at the first week of recovery and then showed a tendency to decrease at the second week. At the second week, however, the hamsters exposed to smoke from strong or medium cigarettes still showed significantly higher counts than the controls, while no significant change was noted in those exposed to smoke from mild cigarettes. These results indicate that the process and duration of recovery after cessation of smoking may depend on the extent of particulate matter impinging on the respiratory tract, so that strong cigarettes would be more hazardous because of greater number and longer retention of macrophages in the lung.