1. The present study examined the effect of an infusion of the dipeptide alanylglutamine or of the corresponding amino acids alanine and glutamine in equimolar amounts (10 μmol min−1 kg−1) on the canine hindlimb exchange of alanine and glutamine in the post-operative anaesthetized dog. In contrast to glutamine, the dipeptide alanylglutamine is stable in aqueous solution and therefore would be a suitable substrate for parenteral nutrition.
2. The infusion of alanylglutamine increased (a) the arterial concentration of alanylglutamine to a plateau level (120 ± 9.5 μmol/l, mean ± sem) 20 min after start of the infusion, (b) the mean arterial alanine concentration from 761 ± 42 to a plateau of 1500–1700 μmol/l (P > 0.01) and (c) the arterial glutamine concentration from 407 ± 51 to a plateau of 1050–1500 μmol/l (P > 0.01). Alanine and glutamine levels were slightly higher (14% and 26%, respectively, NS) in the group receiving the equimolar amount of alanine and glutamine.
3. Infusion of alanylglutamine for 1 h abolished the net efflux of glutamine (from −0.80 ± 0.1 to −0.03 ± 0.2 μmol min−1 kg−1; P >0.05) and invoked a net influx of alanine (from −0.50 ± 0.19 to + 0.27 ± 0.14 μmol min−1 kg−1; P > 0.01). These changes were similar to those achieved when the two amino acids were infused.
4. This study demonstrates that during short-term administration of alanylglutamine or of the corresponding amino acids the nitrogen release from the hindlimb of the anaesthetized post-operative dog via alanine and glutamine is reduced.