The Relationship Between Sodium Fluxes and Electrical Potentials Across the Normal and Inflamed Human Rectal Wall in Vivo

The normal human rectum generates a substantial transmural potential difference (PD), which in vivo is almost unaffected by the intraluminal ionic composition. The relationship between sodium transport and electrical PD across the intact human rectal wall has been studied in three healthy subjects and in eight patients to elucidate the significance of sodium movements in decreasing PD in ulcerative colitis (UC) and Crohn's disease. A linear relationship was found between the log of the ratio for bidirectional sodium fluxes and the transmural PD with a ratio of unity at zero PD. As a significant increase in exsorption and only a moderate but significant decrease in insorption occurred in the patients, the initial changes of sodium transport and PD in inflammatory bowel disease are explained in terms of altered permeability characteristics of the rectal mucosa, probably followed by damage to the active sodium pump. Accordingly, the permeability coefficient of the inflamed mucosa was estimated to be 10 −2 to 10 −3 cm sec −1 , while the diffusional sodium permeability coefficient of normal colonic mucosa was of the order 5 × 10 −6 cm sec −1 .