title: Development, validation, and application of a surrogate analyte method for determining N-acetyl-l-aspartyl-l-glutamic acid levels in rat brain, plasma, and cerebrospinal fluid.
abstract: A bioanalytical strategy for the simple and accurate determination of endogenous substances in a variety of biological matrices using liquid chromatography-tandem mass spectrometry is described. The robust method described here uses two stable isotope-labeled compounds as a surrogate analyte and an internal standard to construct calibration curves with authentic matrices that can be applied to determine N-acetyl-l-aspartyl-l-glutamic acid (NAAG) levels in rat brain, plasma, and cerebrospinal fluid (CSF) using a simple extraction and with a short analysis time of 4min. The validated lower limits of quantification were 1.00nmol/g for brain and 0.0100nmol/mL for plasma and CSF. Using this method, regional differences in NAAG levels in the brain as well as plasma and CSF levels that were much lower than those in the brain were successfully confirmed in treatment-naïve rats. Moreover, after the rats were treated with the intraventricular administration of a NAAG peptidase inhibitor, the NAAG levels increased rapidly and dramatically in the CSF and slightly in the plasma in a time-dependent manner, while the brain levels were not affected. Thus, the procedure described here was easily applied to the determination of NAAG in different matrices in the same manner as that used for xenobiotics, and this method would also be easily applicable to the accurate measurement of endogenous substances in a variety of biological matrices.
authors.affiliation: Pharmacokinetics and Metabolism, Drug Safety and Pharmacokinetics Laboratories, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-Cho, Kita-Ku, Saitama-Shi, Saitama 331-9530, Japan. Electronic address: k-kinoshita@so.taisho.co.jp.
authors.forename: Kohnosuke
authors.initials: K
authors.lastname: Kinoshita
authors.affiliation: Analytical Chemistry, Pharmaceutical Science Laboratories, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-Cho, Kita-Ku, Saitama-Shi, Saitama 331-9530, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Arai
authors.affiliation: Pharmacology 1, Pharmacology Laboratories, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-Cho, Kita-Ku, Saitama-Shi, Saitama 331-9530, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Kawaura
authors.affiliation: Pharmacology 1, Pharmacology Laboratories, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-Cho, Kita-Ku, Saitama-Shi, Saitama 331-9530, Japan.
authors.forename: Tetsuaki
authors.initials: T
authors.lastname: Hiyoshi
authors.affiliation: Pharmacokinetics and Metabolism, Drug Safety and Pharmacokinetics Laboratories, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-Cho, Kita-Ku, Saitama-Shi, Saitama 331-9530, Japan.
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Yamaguchi
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D004151:Dipeptides / Q000097:blood* / Q000134:cerebrospinal fluid*; D008297:Male; D010949:Plasma / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D004151:Dipeptides; C027172:isospaglumic acid
keywords: Biomarker; LC–MS/MS; N-Acetyl-l-aspartyl-l-glutamic acid; NAAG; Peptide; Surrogate analyte