Contribution of luminal concentration of nutrients and osmolality to postprandial intestinal hyperemia in dogs.

Abstract

Intestinal blood flow is increased during digestion. This study assesses if the concentration of nutrients and/or osmolality of chyme in the intestinal lumen are factors determining the hyperemia. Six digested food mixtures containing different concentrations of nutrients and/or having different osmolalities were placed into the jejunal lumen, and their effects on local venous outflow compared. The 100% (999 mOsm/kg), 33% (291 mOsm/kg), and 20% (183 mOsm/kg) food mixtures all increased flow, but the 10% food mixture (94 mOsm/kg) did not. The hyperemic effect of 33 and 20% food was similar, but 100% food produced a greater increase in flow than did 33 or 20% food. Luminal placement of a 30% solution of a nonabsorbable substance polyethylene glycol (1000 mOsm/kg) did not alter flow. Also, the vascular effects of 20 or 10% food mixtures were not altered when these mixtures were made isotonic by the addition of NaCl. These studies indicate that lumen osmolality, within a range of 180 to 1000 mOsm/kg, is not a significant factor contributing to the local hyperemia occurring when nutrients are in the gut lumen. However, the concentration of nutrients in the lumen is a factor determining the local hyperemia.