Amino acid N-acetylation: metabolic elimination of symmetric dimethylarginine as symmetric N(α)-acetyldimethylarginine, determined in human plasma and urine by LC-MS/MS.

Symmetric dimethylarginine (SDMA) is considered as a parameter for renal insufficiency superior to the established creatinine. Its applicability for this purpose may be hampered by the fact that SDMA is not exclusively eliminated via the renal route but is also metabolized. In this work, we present a method for the quantification of the metabolite symmetric Nα-acetyldimethylarginine (Ac-SDMA) by LC-MS/MS in human plasma and urine. D6-Ac-SDMA was used as internal standard. After simple protein precipitation and in-line clean up, the analytes were separated on a porous graphitic carbon column. Calibration functions were linear in the ranges of 0.2-80 nM for plasma and 10-4000 nM for urine. The quantification was matrix independent and the precisions and accuracies were better than 8% at all concentration levels. Concentration found in human plasma and urine was 3.51 nM and 558 nM, respectively, with marked inter-individual differences.