Abstract
We investigated the effects of nitrogen dioxide (NO2), a combustion‐related pollutant reported to depress host resistance to infection, on respiratory patterns in the mouse.
Control mice were exposed to filtered air for 3 days; experimental mice were exposed to 5 ppm NO2 for the same number of days. After exposure, both control and experimental mice were placed in a respiratory monitor and challenged with clean air (0 ppm NO2) or 15, 50, or 100 ppm NO2.
During the challenge with clean air, there were no differences between groups in respiratory rate (RR), tidal volume (TV), or minute volume (MV).
On exposure to NO2, RR increased, whereas TV and MV decreased in both groups. RR increased significantly more in control mice, whereas TV decreased to the same extent. MV decreased significantly more in the NO2 mice.
These results indicate 1) that continual exposure to NO2 for 3 days has no effect on subsequent respiration in clean air, but appears to blunt the irritant response to subsequent exposure to NO2, and 2) that the depressed host resistance reported earlier is not caused by respiratory changes.
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