Analysis of citrulline in rat brain tissue after perfusion with haloperidol by liquid chromatography-mass spectrometry

We have investigated the potential of high-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) to determine enrichments of citrulline as a marker for in vivo nitric oxide (NO) production in brain tissue. The analysis of citrulline as the butyl ester derivative was evaluated using two types of ionization: electron spray ionization (ESI) and atmospheric pressure chemical ionization (APCI). APCI-MS appeared to be more suitable for determination of citrulline than ESI-MS. because the inn intensity of the protonated molecule ion [M+H](+), mit 232, of citrulline in the former was about twelve times higher than in the latter. The chromatography was carried out on a reversed C-8 column with the mobile phase consisting of 15% acetonitrile: 85% H2O: 0.2% acetic acid (v/v). The calibration curve had good linearity within the concentration range investigated (5 ng to 500 ng/ml). The limit of determination was estimated to be ca. 1 ng/ml of standard solution. The method was applied to the analysis of citrulline in the brain dialysate obtained from rat after perfusion of the striatum with haloperidol (HP, 0.1 mM). It is concluded that APCI-MS in combination with HPLC can be successfully applied to determination of citrulline in brain tissue, thus providing a useful tool for assessment of in vivo NO production. (C) 2000 Elsevier Science B.V. All rights reserved.