L-Glutamine (L-Glutamic acid 5-amide), a non-essential amino acid, is synthesized from glutamic acid and ammonia.

L-Glutamine (0.2 and 2 mM) but not D-Gln inhibits the generation of L-Arg by both Arg-depleted and nondepleted endothelial cells. L-Glutamine also inhibits the conversion of L-[14C]Cit to L-[14C]Arg by Arg-depleted endothelial cells. L-Glutamine interferes with the conversion of L-Cit to L-Arg probably by acting on argininosuccinate synthetase rather than argininosuccinate lyase. L-Glutamine also inhibits the generation of L-Arg by the monocyte-macrophage cell line J774 but has no effect on the conversion of L-Cit to L-Arg by these cells. [1] L-Glutamine metabolism stimulates Na+-H+exchange of acid-loaded porcine enterocytes by a mechanism not requiring activation of PKC. [2] L-Glutamine (0.2 mM and 2 mM) but not D-glutamine (2 mM), L-glutamic acid (2 mM) or ammonium chloride (1 mM) also inhibits the generation of L-arginine in endothelial cells. [3] L-glutamine promotes chromatin condensation and formation of crescent-like structures in the nucleus of murine primary microglia as well as of the microglial cell-line BV-2. [4]

L-Glutamine at 0.5, 2 and 5 mM dose-dependently reduces H(2)O(2)- or LPS-induced cell death by 14%, 54% and 95%. L-Glutamine increases Glutamine concentrations in small-intestinal lumen and plasma, reduces intestinal expression of Toll-like receptor-4, active caspase-3 and NFkB, ameliorates intestinal injury, decreases rectal temperature, and enhanced growth performance in LPS-challenged piglets. [5]