Multiple transport pathways for neutral amino acids in rabbit jejunal brush border vesicles

J Membr Biol. 1982;66(3):213-25. doi: 10.1007/BF01868496.

Abstract

Amino acids enter rabbit jejunal brush border membrane vesicles via three major transport systems: (1) simple passive diffusion; (2) Na-independent carriers; and (3) Na-dependent carriers. The passive permeability sequence of amino acids is very similar to that observed in other studies involving natural and artificial membranes. Based on uptake kinetics and cross-inhibition profiles, at least two Na-independent and three Na-dependent carrier-mediated pathways exist. One Na-independent pathway, similar to the classical L system, favors neutral amino acids, while the other pathway favors dibasic amino acids such as lysine. One Na-dependent pathway primarily serves neutral L-amino acids including 2-amino-2-norbornanecarboxylic acid hemihydrate (BCH), but not beta-alanine or alpha-methylaminoisobutyric acid (MeAIB). Another Na-dependent route favors phenylalanine and methionine, while the third pathway is selective for imino acids and MeAIB. Li is unable to substitute for Na in these systems. Cross-inhibition profiles indicated that none of the Na-dependent systems conform to classical A or ACS paradigms. Other notable features of jejunal brush border vesicles include (1) no beta-alanine carrier, and (2) no major proline/glycine interactions.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine / metabolism
  • Amino Acids / metabolism*
  • Animals
  • Biological Transport / drug effects
  • Cell Membrane / metabolism*
  • Diffusion
  • Jejunum / metabolism*
  • Kinetics
  • Lysine / metabolism
  • Male
  • Methionine / metabolism
  • Microvilli / metabolism*
  • Phenylalanine / metabolism
  • Proline / metabolism
  • Rabbits
  • Sodium / pharmacology

Substances

  • Amino Acids
  • Phenylalanine
  • Proline
  • Sodium
  • Methionine
  • Lysine
  • Alanine