Absorption of water, sodium and potassium in small intestine of dogs

Abstract

The rates of movement of isotopically labeled water, sodium and potassium from the contents of segments of duodenum and ileum into the blood (insorption) and from blood to the contents (exsorption) were determined in dogs. The insorption of labeled water and sodium from the duodenal and ileal segments was exponential in character. Calculation of insorption and exsorption using the exponential rate and the Visscher formulation gave similar values. Anesthesia produced by pentobarbital sodium had no effect on the insorption of water and sodium from the intestinal segments, but it caused a small decrease in exsorption into the duodenum. Acidification of the contents of the intestinal segments decreased insorption of water, sodium and potassium, whereas it increased the exsorption of sodium and potassium without altering that of water. The results indicate that the mucosa of the duodenum fulfills the function of equilibrating its contents by maintaining nearly equal and large movements of water and sodium in both directions, while that of the ileum is fixed to serve absorption (a net gain to the body) of water and sodium.