The significance of aerosols in medicine is increased when the distribution
of inhaled aerosols in the different respiratory tract compartments and th
eir interaction with lung structures are known. The aim of this study was t
o investigate the retention of the hydrophobic Teflon spheres used in human
beings so as to analyze their regional distribution and to study their int
eraction with lung structures at the deposition site. Six intubated and ane
sthetized Syrian Golden hamsters inhaled aerosols of Teflon particles with
an aerodynamic diameter of 5.5 mu m by continuous negative-pressure ventila
tion adjusted to slow breathing. Lungs were fixed by intravascular perfusio
n within 21 minutes after inhalation was started, and tissue samples were t
aken and processed for light and electron microscopy. The stereological (fr
actionator) analysis revealed that particle retention was the greatest in a
lveoli (72.4%), less in intrapulmonary conducting airways (22.9%), and the
least in extrapulmonary mainstem bronchi (0.3%) and trachea (4.4%). Particl
es were found submerged in the aqueous lining layer and in close vicinity t
o epithelial cells. In intrapulmonary conducting airways, 21.5% of Teflon p
articles had been phagocytized by macrophages. This study with highly hydro
phobic Teflon particles clearly demonstrates that for spheres of this size,
surface tension and line tension forces rather than the particles' surface
free energy are decisive for the displacement of particles into the aqueou
s phase by surfactant. It was this displacement that enabled subsequent int
eraction with macrophages. Refined knowledge of particle retention may help
us to better understand the biological response to inhaled particles.