Regional clearance of solute from peripheral airway epithelia: recovery after sublobar exposure to ozone

The influence of local exposure to ozone (O-3) On respiratory epithelial pe rmeability of sublobar lung segments was studied by using aerosolized Tc-99 m-diethylenetriamine pentaacetic acid (DTPA; mol wt, 492). Two bronchoscope s were inserted through an endotracheal tube in anesthetized, mechanically ventilated, mixed breed dogs and were wedged into sublobar bronchi located in the right and left lower lobes, respectively. Segments were ventilated v ia the bronchoscope with 5% CO2 in air delivered at 200 ml/min, and an aero sol of Tc-99m-DTPA was generated and delivered through the scope and into t he sublobar segment over a 30-s period. Clearance of Tc-99m-DTPA was measur ed simultaneously from right and left lower lung segments at baseline and 1 , 7, and 14 days after a 6-h sublobar exposure to filtered air or 400 parts per billion O-3 O-3 treatment significantly decreased the clearance halfti me (t(50)) Of (TC)-T-99m-DTPA by 50% from the baseline mean of 32.3 to 16.0 min at 1 day postexposure. After 7 days of recovery, t50 was still reduced by 28.8%; however, by 14 days postexposure, clearance of Tc-99m-DTPA had r ecovered, and the t50 had a mean value of 30.0 min. 99mTc-DTPA clearance wa s not altered by exposure to filtered air, and t50 values were comparable t o baseline at 1, 7, and 14 days postexposure. These results reveal that a s ingle local exposure to O-3 increases transepithelial clearance, but only f ar epithelia directly exposed to OSI and that 7-14 days of recovery are req uired before permeability to small-molecular-weight solutes returns to norm al.