EFFECTS OF CONCENTRATED CIGARETTE-SMOKE ON RESPIRATORY-TRACT CLEARANCE IN THE FERRET

This study was performed to assess the effects of two high concentrati ons (about 380 mg/m(3) and about 38 mg/m(3)) of inhaled cigarette smok e on tracer particle clearance from the head airways region and the th oracic (primarily deep lung) region of ferrets exposed during postnata l 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 b y inhalation, and the clearance rates from the head airways and thorac ic regions were monitored for 78 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 signif icant accelerations of particle clearance rates were observed for the slow-clearing and fast-clearing phases of clearance from the head airw ays region for both the higher and lower concentration groups; the res ults implied a dose-response relationship. Only in the case of the hig her concentration group was significant slowing observed in the thorac ic region analysis, indicating that the head airways region was perhap s the area of greater impact of the smoke aerosol.