Glutamine concentration and tissue exchange with intravenously administered α-ketoglutaric acid and ammonium: a dose-response study in the pig

OBJECTIVE: We investigated the effects of an intravenous load of α-ketoglutaric acid, ammonium (NH4+), and metabolic acidosis on plasma concentration and splanchnic and hindleg tissue exchange of glutamine, glutamate, alanine, and arginine in postabsorptive, anesthetized pigs. METHODS: Sixteen anesthetized piglets received a constant infusion of NH4Cl for 4 h and α-ketoglutaric acid in incremental dosages for 3 h (group 1, n = 8) or a constant infusion of α-ketoglutaric acid for 4 h and NH4Cl in incremental dosages for 3 h (group 2, n = 8). Plasma amino acids were analyzed and splanchnic blood flow was calculated according to the indocyanine green dye infusion technique. Femoral artery blood flow was measured with ultrasound flowmetry. Statistical evaluation of within-group differences was made with the Wilcoxon signed rank test. RESULTS: Plasma glutamine levels increased dose-dependently in group 2 (P < 0.05) but not in group 1. Glutamate concentration increased, mainly in group 2 (P < 0.05), whereas the plasma concentration of alanine decreased in both groups (P < 0.05). Plasma concentration of arginine increased in both groups (P < 0.05). Splanchnic uptake and skeletal muscle release of glutamine did not change in either group compared with baseline values. Splanchnic glutamate release decreased (P < 0.05) in group 1 at 240 min; muscular uptake was unaffected in both groups. Splanchnic uptake and muscular release of alanine were unaffected in both groups. The significance level was set at 0.05. CONCLUSION: Our findings indicate that the splanchnic bed or hindleg skeletal muscle was not the source of the increased plasma concentration of glutamine in this study.