Intestinal blood flow autoregulation during foodstuff absorption

A. P. Shepherd

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

One version of the metabolic theory of autoregulation proposes that tissue oxygenation, not blood flow per se, is the controlled variable. Thus, if oxygen delivery to tissue can be maintained by modulating oxygen extraction, blood flow may change passively with manipulations of perfusion pressure. By contrast, when oxygen extraction is high as in hypermetabolic states, a greater degree of control must be exerted over blood flow if oxygen uptake is to be maintained. To test this prediction, isolated loops of canine small bowel were vascularly perfused as arteriovenous oxygen difference, blood flow, and perfusion pressure were recorded. Pressure-flow curves (P-F) were determined at standardized pressures of 180, 150, 120, 90, and 60 mmHg. In the control situation, P-F autoregulation was weak or absent. In fact, passive responses predominated, i.e., the proportional change in flow was greater than the change in pressure. When metabolic rate was stimulated by placing transportable solutes in the gut lumen, P-F autoregulation became apparent between 120 and 90 mmHg. At the step from 120 to 90 mmHg, flow-regulating mechanisms compensated for nearly 50% of the imposed pressure reduction. In another series of experiments, the effects of elevating venous pressure were studied. In controls myogenic vasoconstriction was absent, but, when metabolic rate was increased, myogenic vasoconstriction followed venous pressure elevations. These data indicate that both metabolic and myogenic mechanisms participate in local control of intestinal blood flow.

Original languageEnglish (US)
Pages (from-to)H156-H162
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume8
Issue number2
DOIs
StatePublished - 1980

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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