The Kinetics of Amino Acid Absorption and Alteration of Plasma Composition of Free Amino Acids After Intestinal Perfusion of Amino Acid Mixtures

Abstract

1) Serial perfusion of the jejunum of normal subjects with equimolar mixtures of 18 l-amino acids containing 1-8 mm of each amino acid revealed a characteristic sequence of absorption for each amino acid and a preferential rate of uptake of certain amino acids. 2) Methionine, isoleucine, leucine, and valine demonstrated the most rapid absorption rates. Other rapidly absorbed amino acids were proline, arginine, alanine, and phenylalanine. Aspartic and glutamic acids were absorbed at the slowest rate. Approximately 83-94% of methionine and the branched amino acids were absorbed. The essential amino acids as a group were absorbed more rapidly than the nonessential amino acids. 3) Valine, isoleucine, proline, leucine, and methionine presented the greatest increase in their plasma concentration following the perfusions of equimolar mixtures. Glutamic and aspartic acids revealed the smallest increase in their plasma concentration. There was some resemblance between the increase in the plasma amino acid concentration and the sequence of amino acid absorption from the equimolar mixtures in the intestine when higher concentrations were perfused. The essential amino acids as a group showed greater rise in their plasma levels than the nonessential amino acids. 4) Following the intestinal perfusions of isonitrogenous amino acid mixtures simulating egg and corn protein, the percetage of each amino acid absorbed was similar for the two food mixtures. The absolute amount of each amino acid absorbed from the protein hydrolysates depended upon its molar concentration in the food mixtures and its characteristic rate of absorption.