Utilization of alanyl-L-glutamine and glycyl-L-glutamine during long-term parenteral nutrition in the growing rat

Utilization of intravenously administered alanyl-L-glutamine and glycyl-L-glutamine as a source of glutamine was tested in growing rats receiving total parenteral nutrition for 15 days. In experiment A the two peptides were compared to each other, in experiment B alanyl-L-glutamine was compared to an equimolar mixture of free alanine and glutamine, and in experiment C glycyl-L-glutamine was tested against an equimolar mixture of free glycine and glutamine.There was no difference of statistical significance in weight gain or nitrogen balance between the respective groups participating in the 3 experiments. Plasma levels of free glutamine were similar during infusion with alanyl-L-glutamine or glycyl-L-glutamine. The daily urinary excretion rate recorded for alanyl-L-glutamine was 3.7% and for glycyl-L-glutamine 4.3% of the infused amount. The results show that both peptides are utilized for protein synthesis and growth to approximately the same as the corresponding free amino acids.