Disposition of protein-bound 3-nitrotyrosine in rat plasma analysed by a novel protocol for HPLC-ECD

金沢大学医薬保健研究域医学系3-Nitrotyrosine (NTyr) is considered as a biomarker of the generation of reactive nitrogen species (RNS). However, it is still difficult to determine its concentration in biological samples. To develop a reliable and high-throughput method, we optimized the conditions for high performance liquid chromatography and electrochemical detection (HPLC-ECD). The best separation of NTyr was achieved using a highly acidic mobile phase (pH 2.5). The concentration of protein-bound NTyr in plasma protein was 593.6 ± 53.8 fmol/mg in rats treated with lipopolysaccharide (LPS) and 114.4 ± 27.6 fmol/mg in control. After intravenous administration of in vitro-nitrated plasma protein, NTyr concentration decreased; the half-life was 63.4 ± 16.8 h. Consistently, protein-bound NTyr concentration in plasma after LPS treatment declined gradually, but was detectable for 1 week. Our protocol is reproducible and suitable for analysing multiple clinical samples to study RNS production in vivo. © 2007 The Japanese Biochemical Society