Absorption of amino‐acids using an in vitro technique

The intestinal absorption of amino‐acid enantiomorphs

“…In vitro experiments. The in vitro intestine preparation of Wiseman (1953) as modified by Smyth & Whaler (1953) was used. Crampton & Smyth (1953) have used this preparation to measure the rate of disappearance of D-and L-alanime from the lumen of the intestine.…”

“…In support of this, Clarke, Gibson, Smyth & Wiseman (1951) showed that L-amino-acids also disappeared faster than D-amino-acids from the Thiry-Vella loop in the dog, and Wiseman (1953) showed with an in vitro technique that L-amino-acids could be transferred by the intestine against a concentration gradient, whereas D-amino-acids could not. While these experiments furnish strong evidence for the existence of a stereochemicaily specific mechanism for absorption of amino-acids from the intestine, they fail to supply any information about the concentration of the D-and L-amino-acids in the blood stream during absorption, and the present work was undertaken to investigate this aspect of the problem.…”

“…While these experiments furnish strong evidence for the existence of a stereochemicaily specific mechanism for absorption of amino-acids from the intestine, they fail to supply any information about the concentration of the D-and L-amino-acids in the blood stream during absorption, and the present work was undertaken to investigate this aspect of the problem. Preliminary accounts of the results have been given by Matthews & Smyth (1952, 1953. …”

Proceedings of the Physiological Society

“…Of great additional interest is the fact that competition between D-and L-enantiomorphs is possible. The experiments of Wiseman (1953) had clearly demonstrated that absorption of a number of L-amino-acids was an active process in that they could be moved against a concentration gradient, but there was no reason to think that any process other than diffusion was concerned with the absorption of D-amino acids. It now seems that this purely passive transfer of D-amino acids is unlikely, and that they share at least part of the mechanism for movement of L-amino acid.…”

Influence of protein sources on performance and plasma amino acid patterns of ruminants

“…In vitro studies have indicated that the rates of re lease of amino acids from dietary proteins may vary (Melnick et al, 1946;• Differences have also been observed in vitro in the rates of absorption of dif ferent amino acids from the intestine (Wiseman, 1953;Friedlander and Quastel, 1955)• It has been shown by Christensen (1949) that the majority of protein is absorbed in to the blood stream as free amino acids and not as peptides.…”