Intermittent inhalation of nitrogen dioxide: Effects on rabbit alveolar macrophages

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Abstract
Rabbits were exposed to 0.3 or 1 ppm NO 2 for 2 h/d and the effects on alveolar macrophages recovered by bronchopulmonary lavage at 3 time points during the exposure series were asessed. 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 NO 2 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 NO 2 . 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 NO 2 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.