EFFECT OF ATROPINE ON MUCOCILIARY TRANSPORT VELOCITY IN ANESTHETIZED DOGS

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Abstract
A radioactive tracer method of measuring mucociliary transport rates (MCTR) in vivo in dogs was recently described. The distance from larynx to carina is measured on inserting a calibrated fiberoptic bronchoscope into the trachea. A small volume (0.04-0.1 ml) of a suspension of radiolabeled albumin microspheres 5-7 .mu.m in diameter is then deposited on the mucosal surface at the carina via a catheter placed through the inner channel of the bronchoscope. The rate of movement of these spheres towards the larynx is visualized sequentially by means of a gamma scintillation camera with a large field of view and is recorded as polaroid images during 10-30 min. By using this technique, transport rates were determined in the tracheas of 10 anesthetized dogs (17 experiments) before and 10 min after i.v. infusion of 0.4 mg of atropine sulfate; each animal served as it own control subject. Baseline MCTR values were determined by using microspheres labeled with 140-KeV 99mTc. After infusion of atropine, MCTR values were again determined using microspheres labeled with 390-KeV 113mIn. Because of their widely differing energy spectrums, both test agents could be used in rapid succession by adjusting the spectrometer of the scintillation camera. MCTR increased in 13 experiments, did not change in 2, and decreased in 2. The percentage increase in MCTR after infusion of atropine was significant as compared to baseline values (30.0 .+-. 0.6%, mean .+-. SE; P < 0.05 by paired t test), as was the absolute chang in MCTR after infusion of atropine (P < 0.05 by 2-way analysis of variance). The effect of atropine in improving mucociliary clearance was quantiatively similar to that previously reported for .beta.-adrenergic agonists.

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