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Physiology Division, Department of Environmental Health Sciences, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205
The influence of
local exposure to ozone (O3) on
respiratory epithelial permeability of sublobar lung segments was
studied by using aerosolized
99mTc-diethylenetriamine
pentaacetic acid (DTPA; mol wt, 492). Two bronchoscopes 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 via
the bronchoscope with 5% CO2 in
air delivered at 200 ml/min, and an aerosol of
99mTc-DTPA was generated and
delivered through the scope and into the sublobar segment over a 30-s
period. Clearance of 99mTc-DTPA
was measured 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
O3.
O3 treatment significantly
decreased the clearance halftime
(t50) of
99mTc-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 99mTc-DTPA had
recovered, and the
t50 had a mean
value of 30.0 min. 99mTc-DTPA
clearance was not altered by exposure to filtered air, and
t50 values were
comparable to baseline at 1, 7, and 14 days postexposure. These results
reveal that a single local exposure to
O3 increases transepithelial
clearance, but only for epithelia directly exposed to
O3, and that 7-14 days of
recovery are required before permeability to small-molecular-weight
solutes returns to normal.
respiratory epithelial integrity; peripheral airway resistance; 99mtechnetium-diethylenetriamine pentaacetic acid
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