Retention of teflon particles in hamster lungs: A stereological study

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.