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标题：Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration
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作者：Leonard, Scott W. ; Gumpricht, Eric ; Devereaux, Michael W. 等
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：2005
卷号：46
期号：05
页码：1068-1075
DOI：10.1194/jlr.D400044-JLR200
出版社：American Society for Biochemistry and Molecular Biology
摘要：To evaluate vitamin E metabolism, a method was developed toquantitate liver ${alpha}$ - and ${gamma}$ -tocopherol metabolites, ${alpha}$ -carboxyethylhydroxychroman [ ${alpha}$ -CEHC; 2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman]and ${gamma}$ -CEHC [2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman],respectively. Vitamin E supraenriched livers were obtained fromrats that were injected with vitamin E daily for 18 days. Liversamples ( $~$ 50 mg) were homogenized, homogenate CEHC-conjugateswere hydrolyzed, CEHCs were extracted with ethyl ether, andthen CEHCs were quantitated using liquid chromatography-massspectrometry (LC-MS). Precision, based on intersample variability,ranged from 1% to 3%. Recovery of ${alpha}$ - and ${gamma}$ -CEHCs added to liverhomogenates ranged from 77% to 87%. Detection limits of ${alpha}$ - and ${gamma}$ -CEHC were 20 fmol, with a linear detector response from 0.025to 20 pmol injected. Corresponding with an increase in liver ${alpha}$ -tocopherol, the MS peak for liver ${alpha}$ -CEHC (mass-to-charge ratio277.8) increased 80-fold (0.18 ± 0.01 to 15 ±2 nmol/g). Liver ${alpha}$ -CEHC concentrations were correlated with serum ${alpha}$ -CEHC, liver ${alpha}$ -tocopherol, and serum ${alpha}$ -tocopherol (P < 0.001for each comparison). ${alpha}$ -CEHC represented 0.5–1% of theliver ${alpha}$ -tocopherol concentration. Thus, LC-MS can be successfully used to quantitate ${alpha}$ - and ${gamma}$ -CEHCin liver samples. These data suggest that in times of excessliver ${alpha}$ -tocopherol, increased metabolism of ${alpha}$ -tocopherol to ${alpha}$ -CEHCoccurs. Abbreviations: CEHC, carboxyethyl hydroxychroman; LC-MS, liquid chromatography-mass spectrometry; MDR1, multidrug resistance protein-1; m/z, mass-to-charge ratio; SXR, steroid and xenobiotic receptor; UGT1A1, UDP-glucuronosyltransferase-1A1 Supplementary key words ${alpha}$ -carboxyethyl hydroxychroman • ${gamma}$ -carboxyethyl hydroxychroman • mass spectrometry • vitamin E metabolism • ${alpha}$ -tocopherol • ${gamma}$ -tocopherol • liquid chromatography-mass spectrometry