Simultaneous quantitative determination of NG,NG-dimethyl-l-arginine or asymmetric dimethylarginine and related pathway's metabolites in biological fluids by ultrahigh-performance liquid chromatography/electrospray ionization-tandem mass spectrometry

BACKGROUND: Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide (NO) formation inhibitor, has emerged as a promising biomarker of NO-associated endothelial dysfunction in cardiovascular diseases as well in chronic renal failure. The interest in potentially fundamental role of this metabolite, in basic and clinical research, led to the development of numerous analytical methods for the quantitative determination of ADMA and dimethylarginines in biological systems, notably plasma, serum and urine. OBJECTIVES: The aim of this work was to present a simple, fast and accurate UPLC-tandem-MS-based method for the simultaneous determination and quantification of arginine, ADMA, SDMA, NMMA, homo-arginine and citrulline. This method is designed for high sample throughput of only 10 \u3bcL of human plasma, serum or urine. METHODS: The analysis time is reduced to 1.9 min by an ultrahigh-performance liquid chromatography run coupled with electrospray ionization (ESI) in the positive mode tandem mass spectrometry detection. RESULTS: The method was validated in plasma, serum and urine. Correlation coefficients (r(2)) of the calibration curves in all matrices considered ranged from 0.9810 to 0.9993. Inter- and intra-assay precision, accuracy, recovery and carry-over were evaluated for validation. The LOD was 0.01 \u3bcM for all compounds in water, plasma and serum and 0.1 \u3bcM in urine. The LOQ was 0.05 \u3bcM for ADMA, SDMA, NMMA and H-Arg and 0.5 \u3bcM for Arg and Cit in water, plasma and serum; while in urine was 0.1 \u3bcM for ADMA, SDMA, NMMA and H-Arg and 0.5 \u3bcM for Arg and Cit. The precision was ranged from 1% to 15% expressed as CV% and the accuracy (bias %) was <\ub17% for all added concentrations with the exception of NMMA (-10%). ADMA mean plasma levels, measured in healthy adults and newborns, were in accord with literature data published: (M\ub1SD) 0.56\ub10.10 \u3bcM and 0.84\ub10.21 \u3bcM, respectively, showing that ADMA levels in plasma decreased with age. In serum we have similar data (0.54\ub10.18 \u3bcM and 1.14\ub10.36 \u3bcM), while in neonatal urine ADMA was 11.98\ub17.13 \u3bcmol mmol(-1) creatinine. CONCLUSIONS: Data from calibration curves and method validation reveal that the method is accurate and precise. The fast run time, the feasibility of high sample throughput and the small amount of sample required make this method very suitable for routine analysis in the clinical setting