Pulmonary Clearance and the Function of Macrophages

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Abstract
The elimi-nation of inhaled SiO2 from rat lungs can be accelerated by suitable use of trypan blue, the dose and time interval between injection of trypan blue and exposure to SiO2 being decisive. It was necessary to administer trypan blue 1-2 days before exposure to mobilize alveolar macrophages. Other stimuli, microinhalation of TiO2, had a similar effect, elimination being increased from 20%-28% to 45%. A total body dose of 300 r irradiation just before exposure to SiO2 inhibited elimination. Irradiation 2 days before exposure had no effect. Results support the assumption that alveolar phagocytosis is the main physiological mechanism preventing penetration of particles deposited in the alveolar space into the pulmonary interstitium.