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.
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