Transport of l-tyrosine by the small intestine in vitro

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Abstract
L-Tyrosine was absorbed against a concentration gradient by sacs of isolated small intestine obtained from several animal species. During absorption the tissue segments accumulated the amino acid to concentrations as high as nine times that in the suspending medium. In the case of the hamster the rate of transport was maximal in the mid portion of the small intestine. Studies on specificity of the transport system showed that l-tyrosine and dl-meta-tyrosine were transported while no activity was observed with d-tyrosine, dl-ortho-tyrosine, and 3,5-diiodo-l-tyrosine. Transport of l-tyrosine was inhibited by l-phenylalanine and l-methionine but not by d-phenylalanine. High tyrosine diet did not alter the rate of the in vitro transport of this amino acid in the rat.