Absorption of free and peptide-linked glycine and phenylalanine in children with active celiac disease.

Using a marker perfusing technique, the jejunal absorption rates of glycine and phenylalanine from test solutions containing either the free amino acids or glycyl-phenylalanine (30 mM each) were studied in five children with active celiac disease and in three controls. Changes in plasma amino acid levels during intestinal loading were also investigated. Mean values of intestinal uptake rates (micromoles/min/20 cm segment) in patients and controls were found to be as follows: free glycine, 19.3 +/- 21.8 and 74.5 +/- 10.3; peptide-linked glycine, 45.0 +/- 12.4 and 110.7 +/- 20,1; free phenylalanine, 33.6 +/- 19.6 and 106.1 +/- 10.6; peptide-linked phenylalanine, 44.5 +/- 14.3 and 113.6 +/- 11.1, respectively. Thus, amino acid absorption is higher from peptide-linked glycine and phenylalanine, and the advantage of individual amino acid absorption from dipeptide seems to be maintained in the disease state. Changes of amino acid levels in plasma do not reflect impaired intestinal absorption because the levels of phenylalanine increased to the same extent in patients and in controls, and the increment of glycine was found to be higher in the patients group.