Intermittent inhalation of nitrogen dioxide: effects on rabbit alveolar macrophages

Rabbits were exposed to 0.3 or 1 ppm NO2 for 2 h/d and the effects on alveolar macrophages recovered by bronchopulmonary lavage at 3 time points during the exposure series were assessed. Cells were examined 24 h after 2, 6, or 13 exposures, i.e., on d 3, 7, and 14. There was no change in the viability or numbers of macrophages recovered at any time, nor was an inflammatory response produced. The ability of macrophages to attach to a surface was not affected by exposure. Random mobility was reduced at d 3 in the 0.3 ppm exposure series, but was not different from control after any of the 1 ppm exposures. The phagocytic index, i.e., the fraction of viable cells able to phagocytize latex particles, was not affected by NO2 exposure. However, phagocytic capacity--i.e., the numbers of phagocytizing cells that internalized specific numbers of particles--was different from control on d 3 with both levels of NO2. At 0.3 ppm, particle uptake was reduced, while at 1 ppm it was enhanced in that a greater fraction of cells contained a large number of latex particles. The results show that phagocytic capacity and random mobility are sensitive indices of response to NO2 and that adaptation to the exposures apparently occurred in that both phagocytosis and mobility returned to control levels by d 7 and remained there through the duration of the exposure series.