Glutamine and citrulline concentrations reflect nitric oxide synthesis in the human nervous system

INTRODUCTIONAlthough citrulline is produced by nitric oxide (NO) synthase upon activation of the NMDA glutamate receptor, nitrite and nitrate (NOx) concentration is considered the best marker of NO synthesis, as citrulline is also metabolised by other enzymes. This study analyses the correlation between human cerebrospinal fluid NOx and citrulline concentrations in order to determine the extent to which citrulline reflects NO synthesis and glutamatergic neurotransmission. METHODSParticipants were patients with acute neurological diseases undergoing lumbar puncture (n=240). NOx and amino acid concentrations were determined by HPLC. RESULTSNOx concentrations did not vary significantly where infection (p=0,110) or inflammation (p=0,349) were present. Multiple regression analysis showed that NOx concentration was correlated with glutamine (r=-0,319, p