Morphometric analysis of focal lung injury caused by low levels of nitrogen dioxide
Abstract
Changes in cells of the terminal bronchiolar epithelium in response to subchronic exposure to 0.5 and 2.0 ppm NO2 were evaluated using morphometric techniques. Oriented sections through the distal portion or randomly selected terminal bronchioles were used to determine the relative number of ciliated and nonciliated (Clara) cells, as well as their mean volume and surface areas. Exposure to 0.5 ppm NO2 caused no detectable changes in either of these types of cells. Exposure to 2.0 ppm caused a 19% reduction in the relative number of ciliated cells. The mean volume of the remaining ciliated cells was slightly increased and there was an 18% reduction in the ciliated surface area/cell. Clara cells were unchanged in number but showed evidence of spreading on the basement membrane surface and a loss of their protuberant dome giving a 23% decrease in the mean luminal surface area/cell.