Glutamine appearance rate in plasma is not increased after gastrointestinal surgery in humans

The metabolic response to surgical stress is characterized by muscle protei n breakdown and mobilization of amino acids and has been postulated to furn ish glutamine and other amino acids to the immune system, gut and liver. Th e present study was undertaken to investigate whether the whole body appear ance rate (R-a)(3) Of glutamine in plasma is increased after major elective surgery. Fourteen patients (8 males, 6 females) were measured prior to lap arotomy and on the second postoperative day. Patients received a primed con tinuous 6-h infusion of L-[5-(15) N]glutamine and L-[1-C-13]leucine, and ar terial blood samples and muscle biopsies were taken for concentration and e nrichment measurements. As expected, the metabolic response to surgery was characterized by a rise in whole body protein breakdown (n = 14, P < 0.001) and a decreased concentration of glutamine in plasma (n = 14, P < 0.001) a nd muscle (n = 8, P < 0.01). However, these catabolic changes were not refl ected by an increase in the plasma R-a of glutamine: 246 +/- 8 mu mol.kg(-1 ).h(-1) before surgery vs. 241 +/- 10 mu mol.kg(-1).h(-1) on the second pos toperative day. We conclude that the whole body R-a of glutamine in plasma is not increased 2 d after elective gastrointestinal surgery. Further studi es are warranted to establish whether the lack of an increase in plasma glu tamine R-a provides a rationale for glutamine supplementation.