AJP - Gastrointestinal and Liver Physiology, Vol 242, Issue 6 541-G546, Copyright © 1982 by American Physiological Society
A model of the mesenteric circulation
E. D. Jacobson, R. H. Gallavan Jr and J. D. Fondacaro
A model of the mesenteric microcirculation is proposed that explains three
observed variations in the hyperemic response of the small intestine to
different dilator stimuli. The model assumes a two-component circulation in
which one component delivers more than enough blood flow and oxygen to meet
the metabolic demands of the resting tissue served by this
"flow-independent component." The second portion, known as the
"flow-limited component" delivers an insufficient blood supply for tissue
needs and, therefore, restricts the metabolism of the parenchyma it serves.
The three types of reported hyperemic responses are a) hyperemia induced by
certain drugs, such as nifedipine and acetylcholine, in which case only the
flow-limited component is dilated and one observes an increase in blood
flow to the gut without any increase in intestinal oxygen consumption; b)
hyperemia induced by stimulating active cotransport of nutrients from the
intestinal lumen, in which case the tissue served by the flow-independent
component increases its metabolism and oxygen demand, resulting in an
increase in oxygen consumption that exceeds proportionately the increase in
blood flow; and c) hyperemia induced by other vasodilator drugs, such as
adenosine, in which case both vascular components are dilated and both
blood flow and oxygen uptake are increased, but the increase in blood flow
is proportionately greater than the increase in oxygen consumption.
