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Deposition and clearance of inhaled aerosol in the respiratory tract of chickens.

Sixteen unanesthetized adult White Leghorn chickens (Gallus domesticus) were exposed to an aerosol of 99mTc-labeled submicrometric particles and killed 0, 1, 12, or 36 h later. The amount and distribution of radioactive particles retained in the lungs and skeletal system were measured to describe regional deposition and clearance. Particles were present in the lungs, air sacs, and skeletal system immediately after exposure. Reduction in activity with time suggested clearance of aerosol from the lungs and pneumatized bones. Aerosol particles were not distributed uniformly within the lungs; there was greater retention in the caudal regions. No dorsoventral gradients were observed. Of the initial lung deposition, 54 +/- 13.9% (SD) remained 1 h postexposure and 35.6 +/- 20.9% remained 36 h later. These data suggest an early fast phase of lung clearance followed by a slower phase. Detailed morphological studies are needed to understand the underlying clearance mechanisms and the bases for the differences in regional deposition.