Pressure and frequency dependent linkage between motility and epithelial secretion in human proximal small intestine

Motor disturbances are sometimes associated with diarrhoea by unknown mechanisms.

To determine if there is a quantitative link between intestinal motility and epithelial secretion.

Experiments were performed in 21 healthy volunteers and three patients with villus atrophy.

Duodenal and jejunal motor activities were registered in the fasted state by open tip manometry. Secretion was measured directly by marker perfusion and indirectly by recording transmural potential difference (PD).

A significant correlation was found between "low pass filtered" pressure and PD, but no correlation was found between amplitudes of isolated contractions and PD changes. During repeated phasic contractions (phase III of migrating motor complex), PD increased at a rate that was higher in the duodenum than in the jejunum, and higher in patients with villus atrophy than in healthy controls. After reaching a peak, PD decreased despite continuing phasic motor activity, provided that there was no concomitant increase in mean pressure. Fluid secretion increased roughly in parallel with PD, except at the very end of the cycle.

To explain these findings, one has to postulate participation of at least two types of receptor: a slowly adapting pressure sensitive receptor and another mechanoreceptor, possibly a mucosal touch receptor, to account for the run down phenomenon. This model predicts that short lasting trains of contractions, so called discrete clusters, will be a particularly potent stimulus for activation of mucosal secretion.