Determination of asymmetrical dimethylarginine by capillary electrophoresis-laser-induced fluorescence

Asymmetric dimethyl-L-arginine (ADMA) is a naturally occurring analogue of L-arginine (L-Arg), the substrate of nitric oxide synthase (NOS). ADMA is a potent endogenous inhibitor of NOS and accumulates in the plasma of patien ts with renal failure, with peripheral arterial occlusive disease or with c linically asymptomatic hypercholesterolemia. We measured circulating concen trations of L-arginine, symmetric and asymmetric dimethylarginine (SDMA and ADMA, respectively) in human serum. We developed a new method for the rapi d determination of these molecules using capillary electrophoresis and lase r-induced fluorescence (CE-LIF). All methylated arginines were labeled with fluorescein isothiocyanate (FITC) prior to analysis. Under the capillary e lectrophoresis (CE) conditions used, methylated arginine derivatives were w ell separated, with a migration time of around 10 min. These migration time s were smaller than the ones of other amino acids which do not have the sam e charge at pH 10. Consequently, such basic amino acids were well separated from most of the other amines or amino acids. Moreover, CE allowed one to separate all the analogues of fluorescein thiocarbamyl-arginine. The result s indicated that CE-LIF is useful as a selective, rapid, cheap and sensitiv e tool for the determination of methylated arginine products. This new tech nology might appreciate the endogenous substrate for NO synthase and facili tate the knowledge of the physiological and pathophysiological regulation o f NO synthesis. (C) 2000 Elsevier Science B.V. All rights reserved.