Absorption of Amino Acids from the Small Intestine of Domestic Fowl

Abstract

A series of experiments was carried out to examine some basic aspects of the in vivo absorption of L-amino acids in the chicken. When an equimolar mixture of 18 L-amino acids was injected into tied-off segments of bird intestine, it was observed that the absorption rate of amino acids was not dependent on their molecular weight; but amino acids with larger nonpolar side chains, such as methionine, isoleucine, valine, leucine, tryptophan and phenylalanine, were absorbed rapidly, whereas glycine and amino acids with polar side chains, such as glutamic acid, aspartic acid and arginine, were absorbed slowly. Amino acid absorption from the intestinal loop in situ was measured using a circulation unit when each of 2 L-amino acids was administered singly or in combination. The results showed that competitive inhibitory effects appeared in amino acid absorption. The absorption of leucine or phenylalanine was inhibited by methionine, but the inhibitory effect of leucine or phenylalanine on methionine absorption was not so great. When methionine was administered with glutamic acid, the absorption of glutamic acid was strongly inhibited, whereas the absorption of methionine was accelerated slightly. It was also observed that glutamic acid increased water absorption.