Am. J. Respir. Cell Mol. Biol., Vol 10, No. 6, 06 1994, 594-603.
The effect of particle inhalation on macrophage number and phagocytic activity in the intrapulmonary conducting airways of hamsters
M Geiser, M Baumann, LM Cruz-Orive, V Im Hof, U Waber and P Gehr
Department of Anatomy, University of Bern, Switzerland.
The number and functions of macrophages in the lungs are crucial factors
for prevention and development of lung disease caused by inhaled particles.
To examine whether airway macrophages are attracted to the site of particle
deposition and what proportion of these macrophages is involved in
phagocytosis, aerosols of 6-microns polystyrene particles (PSP) were
inhaled by Syrian Golden hamsters under controlled conditions through an
inhalation tubule and their lungs were fixed by intravascular perfusion
within 20 min (PSP-1, PSP- 1a), 40 min (PSP-2), and 24 h (PSP-3) after the
beginning of the inhalation. The number and the phagocytic activity of
airway macrophages were studied in situ with a fractionator, a stereologic
method, on light microscopic sections. No significant increase in
macrophage number was detected for the groups PSP-1 and PSP-1a. The
increase for group PSP-2 was, however, between 2- and 3-fold, whereas for
group PSP-3 the increase was between 1.5- and 2.5-fold with respect to
control animals, which had inhaled ambient air through an intubation tubule
(C-2) and whose lungs had been fixed after 40 min. There were no
significant differences among the four groups with respect to the
proportion of airway macrophages that had phagocytized polystyrene
microspheres. Twelve to fifteen percent of the macrophages were found to be
involved in phagocytosis. In the case of the mean number of particles per
phagocytizing macrophage, there was a significant decrease for the PSP-3
group with respect to the pool of the three groups PSP-1, PSP-1a, and PSP-2
taken together. These studies demonstrate (1) that airway macrophages are
rapidly recruited to the sites of particle deposition and (2) that only a
small proportion of very active macrophages contributes to the clearance of
particles, suggesting a great potential of airway macrophages to interact
with many more particles than the hamsters were exposed to in this study.
