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1 Department of Medicine, Duke University, Durham, North Carolina 27710; and 2 Department of Medicine, Johns Hopkins University, Baltimore, Maryland 21224
Airway wall edema, prominent in
inflammatory airways disease, may alter barrier properties at the
airway air-liquid interface such that normal absorption of soluble
substances into the airway circulation is altered. We studied the
effects of bradykinin-induced airway wall edema on the clearance of the
soluble tracer technetium-99m-labeled diethylenetriamine pentaacetic
acid (99mTc-DTPA) from subcarinal airways in sheep
(n = 8). 99mTc-DTPA (6-10 µl) was
delivered by a microspray nozzle inserted through a bronchoscope to a
fourth-generation bronchus both before and 1 h after bradykinin
(20 ml; 10
6 M) had been infused through a cannulated and
perfused bronchial artery. Airway retention (by scintigraphy) and blood
levels of radiolabel were monitored for 30 min after the local
deposition of 99mTc-DTPA. During control conditions,
85-90% of the tracer cleared from the deposition site within 30 min. The maximum blood level during that time was 17% of the total
delivered tracer. However, 1 h after bradykinin infusion, there
was significant retention of the marker at the deposition site with
clearance within 30 min reduced to 63-70% and decreased blood
levels of radiolabel (8%; both P < 0.05). These
results demonstrate that moderate airway wall edema alters blood uptake
and removal of soluble substances delivered to the subcarinal airways.
We suggest that the interplay between vascular and mucociliary
clearance routes will impact the resident time for clearance of soluble
air toxins and/or therapeutic agents from the epithelial surface.
bradykinin; bronchial blood flow; mucociliary transport; soluble-particle clearance; technetium-99m-labeled diethylenetriamine pentaacetic acid
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