Effects of 0.25 PPM Nitrogen Dioxide on the Developing Mouse Lung. Part 2: Quantitation of Elastic Tissue and Alveolar Walls

Abstract

AbstractA colony of 3-wk-old mice (Swiss-Webster) was divided into young adult mice exposed to intermittent 0.25 ppm NO2 for 6 wk and a control group. The left lungs of 186 control and 186 exposed animals were perfused-inflated with glutaraldehyde at 6, 10, and 32 wk post-exposure, and elastic fibers in paraffin sections were stained with aldehyde fuchsin. Image analysis quantitation of elastin content at the first test period showed significant increases in lung elastin for the NO2-exposed animals, that is, fiber number (p = .001), elastin area (p = .007), and elastin alveolar perimeters (p <.008). Internal surface area (alveolar wall perimeters) decreased (p = .05) and lung volume increased slightly but not significantly. There were also nonsignificant trends toward a larger fiber size, and higher elastic fiber/ wall area ratios. A reversal occurred at the 10-wk postexposure test. All elastic fiber measurements for the exposed animals were significantly less than those for the control group, namely, ela...