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Epithelial injury and interstitial fibrosis in the proximal alveolar regions of rats chronically exposed to a simulated pattern of urban ambient ozone.

Publication ,  Journal Article
Chang, LY; Huang, Y; Stockstill, BL; Graham, JA; Grose, EC; Menache, MG; Miller, FJ; Costa, DL; Crapo, JD
Published in: Toxicol Appl Pharmacol
August 1992

Electron microscopic morphometry was used to study the development of lung injury during and after chronic (78 weeks) exposure to a pattern of ozone (O3) designed to simulate high urban ambient concentrations that occur in some environments. The daily exposure regimen consisted of a 13-hr background of 0.06 ppm, an exposure peak that rose from 0.06 to 0.25 ppm, and returned to the background level over a 9-hr period, and 2-hr downtime for maintenance. Rats were exposed for 1, 3, 13, and 78 weeks. Additional groups of rats exposed for 13 or 78 weeks were allowed to recover in filtered clean air for 6 or 17 weeks, respectively. Rats exposed to filtered air for the same lengths of time were used as controls. Samples from proximal alveolar regions and terminal bronchioles were obtained by microdissection. Analysis of the proximal alveolar region revealed a biphasic response. Acute tissue reactions after 1 week of exposure included epithelial inflammation, interstitial edema, interstitial cell hypertrophy, and influx of macrophages. These responses subsided after 3 weeks of exposure. Progressive epithelial and interstitial tissue responses developed with prolonged exposure and included epithelial hyperplasia, fibroblast proliferation, and interstitial matrix accumulation. The epithelial responses involved both type I and type II epithelial cells. Alveolar type I cells increased in number, became thicker, and covered a smaller average surface area. These changes persisted throughout the entire exposure and did not change during the recovery period, indicating the sensitivity of these cells to injury. The main response of type II epithelial cells was cell proliferation. The accumulation of interstitial matrix after chronic exposure consisted of deposition of both increased amounts of basement membrane and collagen fibers. Interstitial matrix accumulation underwent partial recovery during follow-up periods in air; however, the thickening of the basement membrane did not resolve. Analysis of terminal bronchioles showed that short-term exposure to O3 caused a loss of ciliated cells and differentiation of preciliated and Clara cells. The bronchiolar cell population stabilized on continued exposure; however, chronic exposure resulted in structural changes, suggesting injury to both ciliated and Clara cells. We conclude that chronic exposure to low levels of O3 causes epithelial inflammation and interstitial fibrosis in the proximal alveolar region and bronchiolar epithelial cell injury.

Duke Scholars

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Published In

Toxicol Appl Pharmacol

DOI

ISSN

0041-008X

Publication Date

August 1992

Volume

115

Issue

2

Start / End Page

241 / 252

Location

United States

Related Subject Headings

  • Toxicology
  • Rats, Inbred F344
  • Rats
  • Pulmonary Alveoli
  • Ozone
  • Microscopy, Electron
  • Male
  • Fibrosis
  • Epithelium
  • Environmental Exposure
 

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MLA
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Chang, L. Y., Huang, Y., Stockstill, B. L., Graham, J. A., Grose, E. C., Menache, M. G., … Crapo, J. D. (1992). Epithelial injury and interstitial fibrosis in the proximal alveolar regions of rats chronically exposed to a simulated pattern of urban ambient ozone. Toxicol Appl Pharmacol, 115(2), 241–252. https://doi.org/10.1016/0041-008x(92)90329-q
Chang, L. Y., Y. Huang, B. L. Stockstill, J. A. Graham, E. C. Grose, M. G. Menache, F. J. Miller, D. L. Costa, and J. D. Crapo. “Epithelial injury and interstitial fibrosis in the proximal alveolar regions of rats chronically exposed to a simulated pattern of urban ambient ozone.Toxicol Appl Pharmacol 115, no. 2 (August 1992): 241–52. https://doi.org/10.1016/0041-008x(92)90329-q.
Chang LY, Huang Y, Stockstill BL, Graham JA, Grose EC, Menache MG, et al. Epithelial injury and interstitial fibrosis in the proximal alveolar regions of rats chronically exposed to a simulated pattern of urban ambient ozone. Toxicol Appl Pharmacol. 1992 Aug;115(2):241–52.
Chang, L. Y., et al. “Epithelial injury and interstitial fibrosis in the proximal alveolar regions of rats chronically exposed to a simulated pattern of urban ambient ozone.Toxicol Appl Pharmacol, vol. 115, no. 2, Aug. 1992, pp. 241–52. Pubmed, doi:10.1016/0041-008x(92)90329-q.
Chang LY, Huang Y, Stockstill BL, Graham JA, Grose EC, Menache MG, Miller FJ, Costa DL, Crapo JD. Epithelial injury and interstitial fibrosis in the proximal alveolar regions of rats chronically exposed to a simulated pattern of urban ambient ozone. Toxicol Appl Pharmacol. 1992 Aug;115(2):241–252.
Journal cover image

Published In

Toxicol Appl Pharmacol

DOI

ISSN

0041-008X

Publication Date

August 1992

Volume

115

Issue

2

Start / End Page

241 / 252

Location

United States

Related Subject Headings

  • Toxicology
  • Rats, Inbred F344
  • Rats
  • Pulmonary Alveoli
  • Ozone
  • Microscopy, Electron
  • Male
  • Fibrosis
  • Epithelium
  • Environmental Exposure