High-performance liquid chromatographic analysis of muscular interstitial arginine and norepinephrine kinetics - A microdialysis study in rats

Complex interactions between the L-arginine/nitric oxide synthase (NOS) pat hway and the sympathetic nervous system have been reported. Methods capable of measuring L-arginine and norepinephrine (NE) have mainly been reported for plasma. We report the use of the microdialysis technique combined with high-performance liquid chromatography (HPLC) for measurement of both L-arg inine and NE within the same tissue microdialysis sample. The microdialysis probe consisted of linear flexible probes (membrane length: 10 mm, outside diameter: 290 mu m, molecular weight cut-off 50 kDa). The method used for L-arginine measurement was HPLC with fluorescence detection, giving a withi n-run and a between-day coefficient of variation of 2.9 and 12.8%, respecti vely. The detection limit was 0.5 pM/20 mu l injected for L-/D-arginine. Th e method used for ME measurement was HPLC with electrochemical detection. T he coefficients of variation were 4% for within-assay precision and 7.5% fo r between-assay precision. The detection Limit for NE was 1 fmol/20 mu l in jected. The microdialysis technique coupled with HPLC system was validated in vivo to measure muscular interstitial concentrations of both arginine an d NE under baseline conditions and after intravenous infusion of 500 mg/kg of L-arginine or D-arginine. In conclusion, the microdialysis technique cou pled to HPLC allows the simultaneous measurements of both L-arginine and NE within the same tissue microenvironment and will enable the study of the c omplex interactions between the L-arginine/NO pathway and sympathetic nervo us system within the interstitial space of different organs. (C) 2000 Elsev ier Science B.V. All rights reserved.