Combined application of ion-exchange chromatographic methods for the study of "minor basic amino acids"

High-performance liquid chromatographic assay of N(G)-monomethyl-L-arginine, N(G),N(G)-dimethyl-L-arginine, and N(G),N(G)'-dimethyl-L-arginine using 4-fluoro-7-nitro-2, 1,3-benzoxadiazole as a fluorescent reagent

N(G)-Monomethyl-L-arginine (L-NMMA), N(G),N(G)-dimethyl-L-arginine (ADMA), and N(G),N(G)'-dimethyl-L-arginine (SDMA) are emerging cardiovascular risk factors. A high-performance liquid chromatographic method with fluorescence detection for the simultaneous determination of L-NMMA, ADMA and SDMA is described. The assay employed 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) as a fluorescent derivatization reagent. After solid phase extraction with cation-exchange column, the methylated arginines were converted to fluorescent derivatives with NBD-F, and the derivatives were separated within 32 min on a reversed-phase column. Nomega-Propyl-L-arginine was Used as an internal standard. Extrapolated detection limits were 12 nM (12 fmol per injection) for L-NMMA and 20 nM (20 fmol per injection) for ADMA and SDMA, respectively, with a signal-to-noise ratio of 3. The calibration curves for L-NMMA, ADMA and SDMA were linear within the range of 50-5000 fmol. The method was applied to the quantitative determination of L-NMMA, ADMA and SDMA in 200 microl of rat plasma. The concentrations of L-NMMA, ADMA and SDMA in rat plasma were 0.16 +/- 0.03, 0.80 +/- 0.25 and 0.40 +/- 0.21 microM, respectively (n = 5).

Determination of dimethylated arginines in human plasma by high-performance liquid chromatography

Using high-performance liquid chromatography (HPLC) with multigradient elution, N(G),N(G)-dimethyl-L-arginine (asymmetric-DMA, ADMA) and N(G),N'(G)-dimethyl-L-arginine (symmetric-DMA, SDMA) can be separated from human plasma samples. The dimethylarginine compounds in plasma, after extraction with a cation-exchange column, are converted to fluorescent derivatives with o-phthaldialdehyde (OPA) in an alkaline medium and the derivatives are separated simultaneously within 50 min on a reversed-phase column (Ultracarb 3 ODS(20)). The recoveries of ADMA and SDMA are over 80% and the method permits quantitative determination of dimethylated arginines at concentrations as low as 0.1 micromol/l in human plasma.

Determination of N(G),N(G)-dimethylarginine in human plasma by high-performance liquid chromatography

N(G),N(G)-Dimethylarginine (asymmetric dimethylarginine, ADMA) can be directly separated and measured from deproteinized human plasma using o-phthaldialdehyde-mercaptoethanol (OPA reagent) as a fluorogenic reagent by reversed-phase high-performance liquid chromatography. The mean recovery of ADMA was over 96% and the inter- and intra-assay coefficients of variation of amounts were lower than 3.80% and those of retention time were below 0.37% for five runs. The detection limit of the assay is 1 pmol when the signal-to-noise ratio is 3:1. It was observed that the concentration of ADMA was significantly elevated in plasma of patients with pregnancy induced hypertension (PIH) in contrast to healthy pregnant women.

Determination of methylated amino acids in human serum by high-performance liquid chromatography

Employing high-performance liquid chromatography with isocratic elution using a two-column system (mu Bondapak C18 and mu Bondapak CN) and phenyl isothiocyanate as a fluorogenic reagent, NG-monomethylarginine (MMA). NG-dimethylarginines, and epsilon-N-trimethyllysine (TML) can be quatitatively separated from human serum samples. The recoveries of these amino acids were over 90%. It was observed that the serum concentrations of MMA, DMA and TML were significantly elevated in sera obtained from patients suffering from diabetes mellitus, hepatitis or hyperthyroidism, particularly the last condition.

Identification of N-methylated basic amino acids from human adult teeth

NE-monomethyl-lysine, NG-NG'-dimethyl-arginine, and NG-NG-dimethyl-arginine from tooth protein fractions were identified utilizing thin-layer chromatography, amino acid analysis, and gas chromatography. It is suggested that a relationship exists between the presence of these N-methylated basic amino acids and the resting stage of tooth tissue.