Effects of cigarette smoke generated by different smoking machines on pulmonary macrophages of mice and rats

C57BL/6 male mice and Sprague Dawley male rats were exposed to cigarette smoke generated by different smoking machines. Animals inhaled 20% smoke from the Kentucky 2A1 Reference cigarette twice daily 7 days per week for 1 to 5 weeks. Microscopic assessment of lung tissue revealed no abnormal manifestations in animals exposed to smoke in the different smoking machines. However, pulmonary macrophages from lungs of animals exposed to smoke in one of the machines contained crystalline material resembling aluminum silicate. It was determined that this material originated from a structural component of the machine and not from cigarette smoke. It was also observed that smoke generated in the different smoking machines did not elevate equally the intraspecie and interspecie population size of the pulmonary macrophages. The present study points out the need in research dealing with tobacco smoke inhalation for careful evaluation and monitoring of the smoke generation and delivery systems, as well as for awareness of inherent differences in biological responses to smoke among species.