Accumulation and Incorporation of Amino-acid in Rat Intestine in vitro

Abstract

INVESTIGATIONS of the absorption of amino-acids from the intestinal tract have usually been concerned with a single amino-acid or, in some cases, simple mixtures of a few amino-acids^1–3. Under physiological conditions, on the other hand, an initial stage in the assimilation of dietary proteins is the enzymatic liberation during digestion of a mixture composed of peptides and 18–20 free amino-acids⁴. Because of the interactions between the amino-acids in competing for several relatively specific transfer mechanisms, the total rate of absorption of amino-acids from a mixture need not be closely related to the absorption rates of the same amino-acids when measured singly, but will depend on the composition of the mixture present in the intestinal lumen⁴. There is also evidence that during absorption for 1 h of glycine in vitro⁵ and of protein hydrolysate in vivo⁶ there is an incorporation of the absorbed amino-acids into the protein of rat intestinal mucosal cells. This communication records an investigation of amino-acid transport and protein synthesis in rat intestine during absorption of an amino-acid mixture in vitro.