Effects of Concentrated Cigarette Smoke on Respiratory Tract Clearance in the Ferret

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Abstract
This study was performed to assess the effects of two high concentrations (about 380 mg/m3 and about 38 mg/m3) of inhaled cigarette smoke on tracer particle clearance from the head airways region and the thoracic (primarily deep lung) region of ferrets exposed during postnatal respiratory tract development. Ferrets were exposed 2 h/days, 5 days/wk to purified air or to the smoke aerosols starting at 5 wk of age, for a total of 15 wk of exposure. Three weeks prior to the end of the 15-wk exposure regimen, radiolabeled tracer particles were deposited by inhalation, and the clearance rates from the head airways and thoracic regions were monitored for 18 days. The head airways counting data were accurately fit by a double exponential function, reflecting fast-clearing and slow-clearing components. The thoracic counting data were adequately fit by a single exponential function. Statistically significant accelerations of particle clearance rates were observed for the slow-clearing and fast-clearing phases of clearance from the head airways region for both the higher and lower concentration groups; the results implied a dose-response relationship. Only in the case of the higher concentration group was significant slowing observed in the thoracic region analysis, indicating that the head airways region was perhaps the area of greater impact of the smoke aerosol.