Glutamine-mediated nitric oxide synthase inhibition might explain the ‘arginine paradox’

Abstract

• glutamine • nitric oxide • arginine paradox From several studies, it has been described that nitric oxide synthase(NOS) activity increases if extracellular arginine levels are elevated 1, 2 despite of the high intracellular amino acid level (0.1 2 mM in endothelial cells 3 ), which would maintain the enzyme saturated 4. This ‘arginine paradox’ may be explained by several mechanisms including amino acid transport, translational control and the presence of endogenous NOS inhibitors 5, 6.