Effects of Subchronic Inhalation of Low Concentrations of Nitrogen Dioxide. 1. The Proximal Alveolar Region of Juvenile and Adult Rats

摘要

Techniques were devised to isolate tissue from the epithelium of terminal airways and the alveoli proximal to the airways. One day old juveniles and six week old adult rats were exposed to either room air or 0.5 ppm NO2 for 23 hrs per day seven days per week. An additional group of adult rats were exposed to 2.0 ppm NO2 for the same duration. Two daily hour spikes to three times the background levels (0.5 to 1.5 ppm and 2.0 to 6.0 ppm) were applied Mon. through Fri. Morphometric analysis revealed that epithelial injury occurred in all exposed animals. The juvenile rats which had been exposed to 0.5 ppm NO2 exhibited changes in the characteristics of type II epithelial cells. These cells spread to cover more alveolar surface and became thinner. Adult animals exposed to 0.5 and 2.0 ppm NO2 showed changes in alveolar macrophages and in the alveolar interstitium in addition to changes in the epithelium.