A micro‐electrode study of oligopeptide absorption by the small intestinal epithelium of Necturus maculosus.

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Abstract
The effects of some amino acids and oligopeptides on the electrical properties of the brush border membrane of the small intestine of the mudpuppy, N. maculosus, were studied in vitro using microelectrodes. A number of amino acids (glycine, L-proline and L-leucine) and small peptides (carnosine, glycyl-L-proline, L-leucyl-L-leucine, glycylglycine and glycylglycylglycine) depolarized the brush border membrane. This was associated with a reduction of input resistance. Tetraglycine did not appreciably reduce the membrane potential. The electrical effects caused by the application of the peptides are not solely due to the effects of the products of peptide hydrolysis. Furthermore, there appears to be more than a single system available to the peptides. Stereospecificity is found for both amino acids and peptides, but appears to be more marked for the peptides. Peptide-induced depolarizations are less markedly reduced in the absence of external Na+ than are the depolarizations caused by the amino acids. These results are discussed with respect to the mechanism and significance of amino acid and peptide transport in the intestinal tract.