Alanylglutamine reduces muscle loss of alanine and glutamine in post-operative anaesthetized dogs.

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 mumol 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 mumol/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 mumol/l (P greater than 0.01) and (c) the arterial glutamine concentration from 407 +/- 51 to a plateau of 1050-1500 mumol/l (P greater than 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 mumol min-1 kg-1; P greater than 0.05) and invoked a net influx of alanine (from -0.50 +/- 0.19 to +0.27 +/- 0.14 mumol min-1 kg-1; P greater than 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.