The effect of luminal and hormonal factors on small intestinal water and electrolyte transport.

The effects of various biologically active peptides on net jejunal water and electrolyte fluxes were studied in dogs in vivo. Vasoactive intestinal peptide (VIP), gastric inhibitory polypeptide (GIP), glucagon, gastrin, bombesin and neurotensin all had secretagogue activity, while methionine enkephalin stimulated net absorption. Somatostatin had no effect on net basal water and electrolyte transport, but inhibited glucagon-stimulated secretion. Secretin, calcitonin, substance P and pancreatic polypeptide (PP) did not have any effect on net water and electrolyte transport in the doses used in these experiments. The precise role played by these peptides in the control of intestinal transport has still to be determined. Studies in man have confirmed that food in the proximal small bowel stimulates secretion at sites remote from the application of food, and abnormal secretion of some peptides (e.g. VIP) has been associated with diarrhoea. Somatostatin has been used successfully to reduce the volume of certain types of secretory diarrhoea. Methods used in these experiments have been applied to the study of the composition and absorption characteristics of solutions used for oral rehydration in diarrhoea and in exercise-induced dehydration. Glucose polymers have been shown to be absorbed as rapidly as glucose from the jejunum.