Intestinal Absorption of Histidine as Influenced by Tryptophan in the Rat.

Abstract

It has been shown that amino acids have to be available simultaneously and in proper relative concentrations for optimal utilization in the tissues( 1). The first step in the utilization of dietary amino acids is the intestinal transfer to the body proper and therefore the speed and rate of this transfer may significantly influence the simultaneous availability of the amino acids(2). There is only little information available on the mechanism of amino acid absorption. Some data have been published in the literature which suggest that the absorption of amino acids is not a process of simple diffusion, but 4hat some other mechanisms probably some "accelerating factors" may be also involved(3). Further it has been shown by several authors that amino acids are absorbed selectively at varying rates from the gastrointestinal tract. It was the purpose of the present study to determine how the absorption of an amino acid, such as histidine or tryptophan, is influenced by the presence of other amino acids in the intestinal tract.Method. The Cori technic(4) was used to investigate the absorption of amino acids from the gastrointestinal tract of adult male Sprague-Dawley rats. The rats were fed the amino acid solutions via stomach tube. L-tryptophan and dl-phenylalanine were fed as such, and L-'histidine and L-arginine were fed as the monohydTochlorides. All of the amino acid solutions were adjusted to a pH of 7.0-8.0 before feeding. After a predetermined absorption period, the residual amounts of histidine and tryptophan which remained ia the gastrointestinal tract were colonmetrically determined( 5 , 6 ) . The absorption coefficients were computed on a basis of body surface area rather than of body weight in an attempt to obviate any variability due to differences in *This work was supported ,by a grant from the Williams-Waterman Fund of the Research Corporation.the weights of the animals used.For the determination of histidine Lang's modification of the Pauly-Weiss method was used( 5 ) , by which a red color is developed when histidine is treated in alkaline solution with freshly prepared diazotized sulfanilic acid. The only other amino acid giving this oobr under these conditions is tyrosine, which was completely removed by precipitation with HgC12. The test for tryptophan is based on the Voisenet-Rhode reaction ( 6 ) , by which tryptophan specifically produces a blue color in an acidic medium of pdimethylaminobenzaldehyde. In preliminary control experiments it was shown that the presence of tryptophan in the concentrations used did not interfere with the determination of histidine. Similarly, the color test for tryptophan was not modified by the presence of histidine.Results. Table I lists the mean values of the absorption coefficients for histidine and tryptophan t the standard deviations of the mean. Their absorption rates appear to depend to a certain limit on the concentration in which they were fed. The quantity absorbed increased with increasing concentration of the solution fed from 24 till 51) mg/7.5 ml. Greate...

The Levels of Individual Free Amino Acids in the Plasma of Normal Man at Various Intervals After a High-Protein Meal1

“…A number of in vitro studies (28)(29)(30)(31)(32), using mostly the isolated loop of the rat intestine, demonstrate that different amino acids are absorbed at different rates, and that the presence of one amino acid may affect the absorption of another. It may be that in vivo, also, the rate and extent of absorption are not governed entirely by the concentration in the intestine.…”

Absorption of protein digestion products: a review.

“…It is probable that the L-isomers of most, if not all, monoaminomonocarboxylic amino-acids compete with each other for intestinal transport (e.g., Pinsky and Geiger, 1952;Fridhandler and Quastel, 1955;Agar, Hird and Sidhu, 1956;Finch andHird, 1960b,. Hagihira, Ogata, Takedatsu, andSpencer and Samiy, 1961), and that those with long side-chains are the most powerful inhibitors of the transport of other amino-acids within this group.…”

Relationship of blood plasma free amino acids and ingested protein in swine

“…This observation was especially true for soybean protein which can probably be explained by the poor availability of amino acids from this protein or that the rate of absorption of individual amino acids by the small intestine was affected by the presence of other amino acids (Pinsky and Geiger, 1952). Further, it could be that the molar ratios of the amino acids in the intestinal tract are responsible as Delhumeau et al (1962) have presented data indicating that molar ratios influence the magnitude of the percentage of each amino acid absorbed.…”

“…When administered separately each amino acid is absorbed at a characteristic rate (Wiseman, 1955), but this rate may be altered by the presence of other amino acids, suggesting a competition for the transfer mechanism (Pinsky and Geiger, 1952;Hagihira et al, 1960). All L-amino acids are absorbed quite rapidly after digestion and only small amounts of amino acids can be found at any time in the intestinal contents (Hightower, 1962).…”