Glutamine peptide-supplemented long-term total parenteral nutrition: effects on intracellular and extracellular amino acid patterns, nitrogen economy, and tissue morphology in growing rats.

Glutamine (GLN) is a nonessential amino acid that is not included in current regimens for parenteral nutrition because of its chemical instability. This study tested the hypothesis that GLN supplementation during long-term total parenteral nutrition (TPN) (3 weeks) would enhance GLN availability, thereby improving nitrogen economy and growth in a growing rat model: Standard TPN delivering 300 kcal/kg per day (lipid:carbohydrate = 1.1) including 2.1 g of nitrogen per kilogram per day in an all-in-one solution was compared with an isonitrogenous, isocaloric, and isovolemic TPN regimen with 0.29 g of nitrogen per kilogram per day substituted by GLN derived from the dipeptides glycyl-GLN and alanyl-GLN (TPN GLN). Enterally fed controls were included. Analysis was confined to nonbacteremic animals with negative blood culture, in which extracellular and intracellular amino acid concentrations including GLN, nitrogen balance, serum protein concentrations, growth, and histologic sections of liver and small-bowel mucosa (light and scanning electron microscopy) were evaluated. Hepatic intracellular GLN concentrations were significantly lower, in animals receiving GLN-free TPN (11.7 +/- 1.6 nmol/mg fat-free dry and solid tissue mass, n = 9) compared with both GLN-supplemented TPN (16.0 +/- 3.0, n = 7) and enteral feeding (18.2 +/- 1.8, n = 6) (p < .001). Corresponding results were found for intracellular GLN concentrations in skeletal muscle (TPN standard 12.5 +/- 3.1, TPN GLN 14.7 +/- 3.1, enteral control 17.3 +/- 2.3, p < .05), intestinal mucosa, and spleen as well as for plasma concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)