Autoregulation of intestinal blood flow

¹ Department of Physiology, Indiana University School of Medicine, Indianapolis, Indiana

Previous experiments have shown that the arterial vessels of the intestine are responsive to changes in portal venous pressure, with pressure elevation causing arterial constriction. The purpose of the present study was to determine whether these vessels respond in a similar fashion to changes in arterial pressure. In 39 pressure flow studies on segments of terminal ileum, resistance decreased with pressure reduction in 72% of the experiments and increased in 28%. The passive increase in resistance with pressure reduction was seen primarily shortly after the surgical procedure was completed. Thus, it appears that the resistance vessels of the intestine are not ordinarily passively distensible with changes in arterial pressure. As a result of this vascular reaction, the influence of arterial pressure on blood flow is at least partially counteracted. The mechanism of this autoregulation of flow is not a local reflex, a change in interstitial fluid volume, or a change in tone of the intestinal muscle. Changes in concentration of aerobic or anaerobic metabolites, and oxygen tension of the tissues were likewise eliminated. It is concluded that autoregulation of intestinal blood flow is a result of the sensitivity of vascular smooth muscle to change in tension (a myogenic response).

Note:
With the Technical Assistance of Stuart L. Graham

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