AJP - Gastrointestinal and Liver Physiology, Vol 247, Issue 1 13-G18, Copyright © 1984 by American Physiological Society
Clearance of 9-micron spheres and rubidium in the intestinal circulation
S. Gelman, D. N. Granger, K. Fowler and L. R. Smith
Rubidium clearance and 9-micron-sphere entrapment were studied and compared
in isolated intestinal preparations under various physiological conditions
in 10 dogs anesthetized with intravenous pentobarbital sodium. The chosen
intestinal segment was pumped with aortic blood at a constant rate and
pressure of about 90-100 mmHg. The temperature of the isolated loop was
maintained at 37-38 degrees C with an electrical pad. A mixture of 86Rb and
9-micron-spheres labeled with 141Ce was injected into the arterial cannula
supplying the intestinal loop while mesenteric venous blood was collected
for activity counting. Three to four intestinal segments were used from
each dog. The following three experimental conditions were randomly used
for each intestinal segment preparation: 1) a mesenteric venous pressure
(MVP) equaling 0 cmH2O and warmed normal saline infused into the lumen of
segment; 2) an MVP equaling 0 cmH2O and 5% glucose in saline infused into
the intestinal lumen; and 3) the reservoir with venous blood elevated to
provide an MVP equaling 17 cmH2O and warmed normal saline infused into the
intestinal lumen. A very strong and significant correlation was found
between rubidium and microsphere clearances (r = 0.99, P less than 0.0001).
Rubidium extraction was inversely associated with blood flow through the
intestinal segment (r = 0.49, P = 0.02), while microsphere entrapment
(extraction) was independent from intestinal blood flow (r = 0.16). The
data suggest that the shunting of 9-micron spheres through tissue reflects
the arteriovenous shunting of blood and, therefore, can be used as a tool
to study the nutritive and nonnutritive blood flows in tissues.
