The Journal of Membrane Biology

, Volume 53, Issue 1, pp 45–53

Lysine transport across the small intestine. Stimulating and inhibitory effects of neutral amino acids

  • B. G. Munck
Article

DOI: 10.1007/BF01871171

Cite this article as:
Munck, B.G. J. Membrain Biol. (1980) 53: 45. doi:10.1007/BF01871171

Summary

The ordinary aliphatic, neutral amino acids and phenylalanine have been examined for cis-inhibition of influx of alanine (Jmcala) and lysine (Jmclys) and trans-stimulation ofJmclys across the brush border membrane of rat small intestines: and their effects on the unidirectional mucosa-to-serosa flux (Jmslys) across the short circuited intestine have been studied. The effects of alanine, α-amino-n-butyric acid, leucine, and methionine on the steady-state epithelial uptake of lysine [Lys]c have also been measured. In addition the trans-effects of alanine and leucine have been examined for sodium-dependence, and alanine was tested as trans-stimulator of influx of galactose across the brush border membrane (Jmcgal).

All the neutral amino acids were found to be competitive cis-inhibitors ofJmclys, and all, except isoleucine, were trans-stimulators ofJmclys. The magnitude of the trans-effect was unrelated to the efficiency of the amino acid as cis-inhibitor. As illustrated by alanine, the trans-effects are probably completely sodium-dependent. Alanine was also effective as trans-stimulator ofJmcgal. With respect to effects on [Lys]c andJmslys the neutral amino acids fall into two groups: One which reduces [Lys]c and stimulatesJmslys, and one which increases [Lys]c and relatively inhibitsJmslys. These effects are not correlated with the affinities of the neutral amino acids for the two carriers involved.

It is proposed that the trans-effects onJmclys are induced by an electrogenic, sodium-coupled efflux of the neutral amino acid across the brush border membrane, that the stimulation ofJmslys is brought about by a selective stimulation (of unknown nature) of efflux of lysine across the basolateral membrane (Jcslys), assisted by competitive inhibition of lysine efflux across the brush border membrane (Jcmlys), and that the amino acids which do not stimulateJcmlys increase [Lys]c by competitively inhibitingJcslys andJcmlys.

The inhibitory effect of the neutral amino acids onJmclys support the view that the carrier of basic amino acids serves as a second carrier of these amino acids.

Key words

Intestinal transport small intestine lysine neutral amino acids 

Copyright information

© Springer-Verlag New York Inc. 1980

Authors and Affiliations

  • B. G. Munck
    • 1
  1. 1.Institute of Medical Physiology, Department AUniversity of Copenhagen, The Panum InstituteCopenhagen NDenmark