Short-term effects of sidestream smoke on respiratory epithelium in mice: cell kinetics

Male strain A/J and C57BL/6 mice were exposed on five consecutive days, for 6 hr a day, to sidestream smoke generated from Kentucky 1R4F reference cigarettes. Chamber concentrations were 1 mg/m3 of total suspended particulate matter and 528 to 549 micrograms/m3 of nicotine. Cumulative labeling indices in the airways and in the pulmonary parenchyma were measured following 1, 3, or 5 days exposure to unfiltered or filtered sidestream smoke. A significantly increased labeling index was found in A/J mice in the epithelium lining large intrapulmonary airways and terminal bronchioles after 3 and 5 days exposure to unfiltered smoke, whereas following exposure to filtered smoke labeling indices remained normal. The alveolar labeling index was not increased following smoke exposure. In C57BL/6 mice, sidestream smoke did not produce signs of increased cell proliferation in the respiratory tract. It is concluded that the response to sidestream smoke inhalation in mice may depend upon the strain of mice examined.