The effect of ozone and simulated high altitude on murine lung elastin: quantitation by image analysis

Four subgroups of a colony of 50 mice were housed in environmental chambers supplied by particle- and pollutant-filtered air. The animals were exposed to 0.35 ppm ozone and/or simulated high altitude (380 mm Hg) for four weeks, with exposure 4 1/2 hours/day and 5 days/week. Lung elastin area and alveolar wall area were quantitated by computer assisted image analysis of paraffin embedded sections stained with aldehyde fuchsin and metanil yellow. Compared to the controls, the combination of ozone and simulated high altitude resulted in a 54.5% increase in lung elastin area (p less than 0.005), and simulated high altitude by itself increased elastin area by 19.6% (p less than 0.05). Simulated high altitude with and without ozone exposure also increased alveolar wall area (24.8%, p less than 0.01; and 9.7%, NS, respectively). Ozone exposure alone had a reverse effect: a 16.1% decrease in elastin area (p less than 0.1), and a 6.5% decrease in alveolar wall area (NS). Since an intact lung scaffolding is required for full restoration of injured alveolar epithelium and since intact lung elastin is critical for proper lung compliance, the results suggest that ozone exposure at high altitude is most likely to have an adverse effect on lung structure and function.