Water and electrolyte movements across the duodenal mucosa in laying hens during in vivo perfusion]

The net water movements through the duodenum in laying hens are directly dependent on the applied osmotic gradient. The passive water permeability (Lp) of the mucosa is 6 times higher during absorption (mucosa to serosa: 70 microliter/h/mOsm) than in the opposite direction (secretion: 11.5 microliter/h/mOsm) and its semi permeability is 0.49 (reflexion coefficient sigma). Net sodium and potassium movements seem to be linked to net water flux. Duodenal water absorption should not be explained by a process of passive permeability.