The effects of feeding on blood flow to the stomach, small bowel, and colon of the conscious dog

A double-isotope, microsphere technique was used to study the effect of feeding on the distribution of blood flow to the different tissue layers of each part of the alimentary tract of conscious dogs. Flow measurements were obtained 45 min after ingestion of a high-protein meal, at which time the bulk of the meal was in the stomach and jejunum, little or no meal was in the ileum, and no meal was in the colon. Blood flow to the whole wall of the body of the stomach, jejunum, and ileum increased by 96%, 93%, and 153%, respectively, while there was no significant change in flow to the colon. Cardiac output was unchanged by feeding; therefore a much higher fraction of the cardiac output was diverted to the mesenteric circulation. Although the villi presumably carry out most of the work of absorption, all tissue layers in the small intestine (villi, crypts, and submucosa plus muscularis) shared equally in the enhanced postprandial flow. In contrast, the entire increase in flow to the stomach and colon was diverted to the mucosa. These studies indicate that the postprandial increase in gut blood flow is not mediated solely by the local presence of nutrients in the lumen but rather that the presence of food in the upper gut results in a diffuse decrease in vascular resistance along the entire linear extent of the bowel. The proportional increase in flow to all layers of the small intestine suggests that local distribution of flow in this organ is not closely linked to the metabolic demands of the absorptive process.