Abstract

Perfusion experiments in the small intestine of normal subjects and in the ileum of patients with ileostomies demonstrated that the distribution of potassium across the mucosa was compatible with a passive process for transport. In the jejunum potassium transport was shown to be markedly influenced by solvent drag and the jejunal mucosa appears to be more permeable to potassium than to sodium. This permeability was apparently unaffected by calcium in the lumen in concentrations of between 1·15 and 7·25 m-equiv/1. In the ileum potassium transport was influenced by changes in luminal sodium concentration and it is suggested that this is a passive consequence of the change in electrical potential which the change in sodium concentration induces. The electrical potential is thought to be a sodium diffusion potential. All the evidence thus points to a purely passive behaviour of the small intestine towards potassium.