Rates of absorption and the movement of P32 through the intestine of adult rats were measured. These two measurements were combined mathematically to estimate the effective contribution of each segment of the intestinal tract toward normal absorption of phosphorus. All parts of the intestinal tract were able to absorb P32. The rate of absorption was greatest at the duodenum, followed by the jejunum, ileum, colon, and stomach in decreasing order. However, since P32 passed rapidly through the duodenum and jejunum, less material was available to be absorbed, with the result that absorption was less effective in these segments than it was in the ileum. When the progress and rate of absorption was combined quantitatively, the greatest effective absorption was found to occur in the ileum (which absorbed 38% of the total), followed by the duodenum (29%), jejunum (25%), and colon (8%). Two factors were found to limit P32absorption: (a) movement of the isotope into gut segments having slower absorption rate, and (b) decreased absorption of P32 in each gut loop with time. Similar factors had been found previously to limit Sr89 absorption.
THE RATE OF ABSORPTION OF GLUCOSE FROM THE INTESTINAL TRACT