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DISTRIBUTION OF INJURY AND MICRODOSIMETRY OF OZONE IN THE VENTILATORY UNIT OF THE RAT
Citation:
Pinkerton, K., R. Mercer, C. Plopper, AND J. Crapo. DISTRIBUTION OF INJURY AND MICRODOSIMETRY OF OZONE IN THE VENTILATORY UNIT OF THE RAT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-94/050.
Description:
The distribution of ozone-induced injury across the ventilatory unit was determined and compared to a predicted distribution of ozone dose across the some units in order to evaluate dose-response relationships. prague Dawley rats were exposed to either 0.98 ppm ozone 8 hr/day for 90 days or to filtered air only and lungs from both groups examined immediately following the end of exposure. n blocmicrodissection was used to identify and isolate in longitudinal profile the bronchiole-alveolar duct junction, first pair of alveolar duct generations and intervening bifurcation ridge in order to obtain consistent and comparable longitudinal sections across each ventilatory unit the first alveolar outpocketing along the bronchiolar wall of each isolation was identified and used to identify the center of a se(ies of concent6c arcs radiating outward at 1 00 um intervals across each ventilatory unit. he intercept lengths of each arc with the tissue of alveolar septal tips (edges) and alveolar walls were measured and expressed as a function of distance into the ventilatory unit. oth the septal edges and alveolar walls to a depth of 600 um into ventilatory units of animals exposed to ozone were found to be significantly thicker than were the corresponding structures in animals exposed only to filtered air. elative ozone dose across the ventilatory unit was estimated using the geometry of the tracheobronchial tree and the volume and surface area distribution within individual ventilatory units. his mathematical model of the distribution of ozone dose demonstrated a high degree of correlation to the measured tissue injury response. his suggests that the distribution of ozone-induced injury across the alveolar region is primarily determined by the dose distribution rather than being significantly influenced by differences.in tissue sensitivity across the ventilatory unit. he findings of this study demonstrate that microdosimetry and microtoxicology con be carried out to determine dose-response relationships within the ventilatory unit and to assess questions of tissue sensitivity to injury.