THE ABSORPTION OF INORGANIC PHOSPHATE FROM THE SMALL INTESTINE OF THE RAT

Abstract

1. The net absorption of inorganic phosphate has been measured in the jejunum and ileum of male albino rats.2. The net absorption rate of inorganic phosphate increased with decreasing hydrogen‐ion concentration. No optimum value for absorption was found in the pH range 4·4 to 7·9.3. Increasing the concentration of phosphate in the intestinal lumen increased the net absorption rate linearly. No evidence for a rate‐limiting process was found.4. The absorption rate of phosphate was relatively uninfluenced by the tonicity of the intestinal contents, but was greatly diminished in the presence of low concentrations of sodium.5. The presence of 37 mM/l. glucose in the intestinal contents had no effect on the net absorption of phosphate.6. Inorganic phosphate was absorbed more rapidly from the jejunum than from the ileum: the difference in rate may be accounted for by the difference in mucosal area between the two regions.