The low nanomolar levels of N-G-monomethylarginine in serum and urine of patients with chronic renal insufficiency are not significantly different from control levels

There are no reliable mean values of N-G- monomethylarginine (NMMA) in blood and urine of patients with renal insufficiency available in the literature. Therefore we investigate whether the NMMA levels are changed in blood and urinary excretion of nondialysed and dialysed patients with chronic renal insufficiency to evaluate whether NMMA may reach sufficiently increased concentrations in blood of the patients to exert toxic biological activity. In nondialysed as well as in dialysed patients we find no significant difference in serum concentration of NMMA between patients and controls. In nondialysed patients (all with a residual creatinine clearance lower than 15 ml/min), we find 94.5 +/- 26.1 nM (mean +/- SD) versus 94.6 +/- 19.5 nM in controls. Similar levels are found in serum of haemodialysed patients (each with serum creatinine levels >700 muM): 83.0 +/- 20.2 nM. The urinary excretion of NMMA in nondialysed patients is also not significantly different from the excretion of controls: 123 +/- 110 in patients versus 157 +/- 117 nmol/24 hrs in controls. Furthermore, the clearance of NMMA is much lower compared to the clearance of the dimethylarginine derivatives. Based on the literature, the low nanomolar levels of NMMA found in blood of patients with renal insufficiency do not support the statement that NMMA proper may act as a uremic toxin.