We describe a sensitive, simple and convenient stable isotope dilution assay developed to study endogenous metabolism of administered stable isotope-labeled phenylalanine (Phe) in phenylketonuric (PKU) mice treated experimentally with phenylalanine ammonia lyase (PAL). Mouse urine and plasma containing endogenous and administered labeled Phe together with internal standard Phe bearing a different pattern of labeling are converted by in situ diazotization to 2-chloro-3-phenylpropionic acid (CPP). A single solvent extraction is then used to isolate the isotopomers of CPP along with the trans-cinnamic acid (TCA) produced from Phe by PAL, as well as the TCA metabolites benzoic and hippuric acids. This procedure eliminates the need for a separate ion-exchange isolation step for Phe on a second sample aliquot and separate GC-MS analysis. Extracted CPP and the Phe metabolites are then measured by conversion to the pentafluorobenzyl esters and a single analysis by electron capture negative ion GC-MS. The estimated lower limit of quantitation is 0.1 µM. Copyright © 2007 John Wiley & Sons, Ltd.
我们描述了一种灵敏、简单和方便的稳定同位素稀释测定法,该测定法用于研究
苯丙酮尿症(PKU)小鼠体内稳定同位素标记的苯丙
氨酸(Phe)的内源性代谢。含有内源性和给药标记 Phe 的小鼠尿液和血浆以及具有不同标记模式的内标 Phe 会通过原位重氮化转化为
2-氯-3-苯基丙酸(CPP)。然后用单一溶剂萃取法分离出 CPP 的同素异形体、PAL 从 Phe 生成的反式
肉桂酸(
TCA)以及
TCA 代谢物
苯甲酸和
马尿酸。这种方法无需在第二份等分样品上对 Phe 进行单独的离子交换分离步骤,也无需进行单独的 GC-MS 分析。提取的 CPP 和 Phe 代谢物通过转化为五
氟苄基酯和电子捕获负离子气相色谱-质谱(GC-MS)进行一次性分析。估计定量下限为 0.1 µM。Copyright © 2007 John Wiley & Sons, Ltd. All Rights Reserved.