Polystyrene microspheres decrease bronchial artery resistance in
anesthetized sheep.
Pearse, David B., Henry E. Fessler, Elizabeth M. Wagner.
Division of Pulmonary and Critical Care Medicine, The Asthma and
Allergy Center, The Johns Hopkins Medical Institutions, Baltimore, MD
21224
APStracts 2:0150H, 1995.
The use of microspheres to measure tissue blood flow requires that the
microspheres themselves do not alter regional arterial tone. To
determine if microspheres affected bronchial artery resistance, we
cannulated and perfused the bronchial artery in anesthetized sheep.
In 7 sheep, the change in bronchial artery pressure at constant flow
was recorded during infusion of 5 doses (1x105, 2x105, 5x105, 1x106,
and 1.5x106) of 15 [mu] microspheres. Microspheres produced a dose
-dependent, self-limited decrease in bronchial artery pressure
(1.5x106 microspheres decreased bronchial artery pressure by 36% for
31 min). This was a decrease in bronchial artery resistance as
evidenced by a shift in the slope, but not the intercept, of a
pressure-flow curve (n=4). Left atrial injection of 1x107
microspheres decreased bronchial artery resistance by 17% in 6 sheep
with intact bronchial arteries in which flow was measured by
ultrasound probe. The adenosine receptor antagonist, 8-phenyl
theophylline attenuated the fall in resistance by 79% (n=4).
Cyclooxygenase inhibition by indomethacin attenuated the response by
37% (n=4). These results suggest that microspheres caused the release
of adenosine and a vasodilator prostaglandin. Repetitive measurements
of bronchial blood flow by microspheres could overestimate true
bronchial blood flow if the interval between measurements is less
than 30 minutes.
Received 17 February 1995; accepted in final form 28 March 1995.
APS Manuscript Number H151-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 19 April 1995.