Intracellular study of ionic events underlying intestinal membrane transport of oligopeptides

It is now clear that after a protein meal much of the alpha-amino nitrogen which is absorbed from the small intestinal tract is transported into the intestinal epithelium across the brush border membrane of the enterocyte in the form of oligopeptides rather than free amino acids. We report here the results of electrophysiological experiments using intracellular microelectrodes which allow us to add important information concerning the mechanism of membrane transport which must underlie oligopeptide absorption, in particular with respect to the role of Na+ in this peptide transport. Such experiments not only reveal the energetics involved in the major pathway for protein absorption from the gastrointestinal tract but may also be important for understanding the mechanism of action of small peptides in quite different cells, such as the Na+-sensitive binding of the neurohormone oligopeptide enkephalin to the enkephalin receptors in the central nervous system.