Water-ionic shifts and absorption in relation ot intraintestinal hyperosmolality in the rat.

In the rat, a recirculating intestinal perfusion model has been used for a combined study of absorption and transmucosal water-ionic shifts related to intraluminal hyperosmolality. Passive absorption of iodide and active absorption of selenomethionine were not inhibited by intraluminal hyperosmolality. The jejunum was demonstrated to have a greater capacity than the ileum to equilibrate intraluminal hyperosmolality by dilution and to supply its content with cations. The main net movement of sodium into the intestinal lumen was independent of net fluid volume shifts, but constant and specific with respect to time and intestinal level. The experimental model and the findings have been discussed in relation to absorption and obstructive ileus.