AJP - Gastrointestinal and Liver Physiology, Vol 254, Issue 2 156-G161, Copyright © 1988 by American Physiological Society
Histamine or adenosine blockade alters intestinal blood flow autoregulation in swine
N. M. Buckley, S. Diamant, I. D. Frasier and K. Owusu
Department of Physiology and Biophysics, Albert Einstein College of Medicine, New York, New York 10461.
The possible role of histamine or adenosine in intestinal blood flow
autoregulation in 1-mo-old swine was examined by obtaining pressure-flow
relationships before and during intestinal histamine H1- or
adenosine-receptor blockade in two groups of fasting animals under
anesthesia with pentobarbital sodium (30 mg/kg). Changes in abdominal and
thoracic aortic pressures and in superior mesenteric and left renal
arterial flows were recorded during controlled aortic compression above the
celiac artery. After control intestinal and renal pressure-flow
relationships were obtained, a test dose of agonist (0.1 microgram
histamine or 0.2 microgram adenosine/kg body wt) was given into the
superior mesenteric artery. Then an intra-arterial infusion of blocking
agent was started (0.1 mg.kg-1.min-1 chlorpheniramine or 10 mumol/min
theophylline). Degree of blockade was assessed with doses of agonist given
before and after a second set of intestinal and renal pressure-flow
relationships was obtained. Complete blockade of intestinal vascular
histamine H1-receptors with chlorpheniramine abolished, and incomplete
blockade of adenosine-receptors with theophylline attenuated, intestinal
blood flow autoregulation. Renal blood flow autoregulation remained at its
control level. These results indicate that both histamine and adenosine are
among the physiological vasodilators contributing to intestinal blood flow
autoregulation when arterial pressure is decreased in young swine.
