Abstract

Background—The significance of Na-nutrient cotransport induced alterations in paracellular permeability is controversial. Most previous studies have measured intestinal permeability using in vitro methods or in vivo methods immediately after surgical bowel manipulation, and therefore may not be applicable to normal physiological conditions.

Aims—To determine whether activation of Na coupled nutrient transport increases intestinal permeability under normal physiological conditions.

Methods—The effect of Na-nutrient cotransport on intestinal permeability was measured in unrestrained, unanaesthetised, chronically catheterised male Sprague-Dawley rats using two different methods: measurement of the rate of absorption of passively absorbed hexoses, mannitol and l-glucose; and measurement of the mannitol:urea diffusion ratio.

Results—l-Glucose and mannitol absorption were not increased in the presence ofd-glucose, alanine, maltose, or peptides. The mannitol:urea diffusion ratio was not increased by the presence ofd-glucose. The presence of d-glucose in the intestinal lumen for 20 minutes did not alter intestinal permeability.

Conclusions—Under normal physiological conditions, Na coupled nutrient transport does not increase intestinal permeability.