Renal control of intestinal sodium and water transport in the dog

The influence of an intravenous infusion of saline on the absorption of water and sodium by the jejunum has been investigated in dogs previously submitted to sodium-rich or poor diets. While the net intestinal transport was reduced in sodium-loaded animals, no response was observed in the sodium-deprived dogs, despite identical changes in arterial pressure, intravascular volume and blood dilution indexes. The intestinal response of sodium-deprived dogs became positive after transplanting to their neck vessels the kidneys removed from sodium-loaded animals, thus demonstrating that the presence in the blood of a humoral message of renal origin is required to permit the inhibition of net transport. The difference of the responses depended on the variations of the mucosa-to-serosa unidirectional flux. The net potassium transport did not change significantly. The experimental conditions made unlikely an interference of mineralocorticosteroids, angiotensin or antidiuretic hormone. The present results suggest that the kidney might modulate sodium transport in the jejunum, and perhaps elsewhere in the body, by the way of an additional endocrine function.