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 chromatograph y (HPLC) coupled to mass spectrometry (MS) to determine enrichments of citr ulline as a marker for in vivo nitric oxide (NO) production in brain tissue . The analysis of citrulline as the butyl ester derivative was evaluated us ing two types of ionization: electron spray ionization (ESI) and atmospheri c 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 ca rried 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 go od 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 s olution. The method was applied to the analysis of citrulline in the brain dialysate obtained from rat after perfusion of the striatum with haloperido l (HP, 0.1 mM). It is concluded that APCI-MS in combination with HPLC can b e 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.