HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ASSAY FOR THE QUANTITATION OFL-ARGININE IN HUMAN PLASMA

L-Arginine is metabolized to nitric oxide by nitric oxide synthase, an d abnormalities in nitric oxide production have been implicated in the pathogenesis of some diseases involving the vasculature, Thus, there has been interest in the effects of pharmacologic doses of L-arginine in patients with cardiovascular and renal diseases. To study the dispo sition of exogenous doses, an HPLC method was developed to analyze pla sma samples for L-arginine, The assay involves precolumn derivatizatio n of arginine with naphthalenedicarboxaldehyde and cyanide followed by HPLC with UV detection. Only a simple deproteinization of the plasma samples was required, The derivatized arginine was stable (less than 5 % degradation in 20 h), facilitating batch sample processing and analy sis in an autosampler. Calibration curves were generated in Ringer's l actate solution instead of plasma to correct for endogenous plasma L-a rginine. Recovery in plasma, compared to Ringer's solution (n = 4), wa s 103%. Mean intraday assay precision (n = 6), expressed as coefficien t of variation, was 3.4%. Interassay precision (n = 6) was 7%. The ass ay was applied for the quantitation of L-arginine in plasma samples fr om a normal subject who had been given a single oral (10 g) and a sing le intravenous dose (30 g) of erogenous L-arginine.