1981 Volume 16 Issue 5 Pages 313-327
The purpose of this study is to observe the histological changes of the lungs of male Wistar rats exposed continuously to 20 ppm NO2 for 20 hours and to 0.5 ppm NO2 for 19 months.
After the interuption of exposure of high concentration of NO2, blebbing of the Type I cells was observed at the 1st day. 15 to 30 days later, the alveolar intermediate type cells appeared, which represent the transformation of Type II cells to Type I cells.
The number of the Type I and Type II cells was countered. The ratio of the Type II cells to Type I cells increased on the 5 th day, reached the maximum on the 15 th day, and then returned to normal on the 30 th day. The alveolar intermediate type cells were remarkable in this period.
The pinocytotic vesicles of capillary endothelial cells became remarkable at an early stage. And then the pulmonary interstitial tissue became edematous, while no histological changes of junction of endothelial cells was found out during the experiment in each stage. And the disappearance of edema of interstitial connective tissue needed for about 30 days.
The changes in alveolus after the long term exposure to low concentration of NO2 were as follows. After the exposure for 2 months, hypertrophy and increase of Type II cells and the increasing permeability of capillary endothelial cells were observed. And after exposure for 4 months, the edema of pulmonary interstitial connective tissue was observed. These changes had been continuously increasing for 19 months. These changes of the lung after the long term exposure to low concentration of NO2 resemble to the progressive changes of it after the exposure of high concentration of NO2.
