PULMONARY EFFECTS OF PROLONGED OZONE INSULT IN RATS - MORPHOMETRIC EVALUATION OF THE CENTRAL ACINUS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 43  (2) , 108-115
Abstract
Groups of Sprague-Dawley rats were exposed to 0.2, 0.5 or 0.8 ppm of O3 [the principal oxidant gas of photochemical smog] 8 h a day for 20, 50 or 90 consecutive days to evaluate the prolonged effect of oxidant exposure on the centriacinar area of the lung. Morphologic evaluation revealed that epithelial changes and accumulations of macrophages in centriacinar regions at 90 days were similar to but less severe than lesions seen at 7 days. Quantification of inflammatory cells in centriacinar regions using scanning electron microscopy revealed a 5-fold increase above controls after exposure to 0.8 ppm of O3 for 20 days. Both the 0.5- and 0.8-ppm exposure groups had significantly (P < 0.05) increased numbers of inflammatory cells within proximal alveoli at all time periods. Morphometric analysis applied to transmission electron microscope micrographs demonstrated that the arithmetic mean thickness of the air-blood barrier was 1.20 .+-. 0.13 .mu.m (mean .+-. SD) in controls; 2.92 .+-. 0.92 .mu.m and 2.17 .+-. 0.18 .mu.m in rats exposed to 0.8 ppm O3 for 20 or 90 days, respectively. The increased thickness was accompanied by an increase in the relative volume of the interstitium. Centriacinar lesions induced by O3 diminish with continued exposure, but significant morphologic alterations do persist through 90 days of exposure at the 0.5- and 0.8-ppm levels but not at the 0.2-ppm O3 level.

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