Biochemical changes in postmortem brains of Alzheimer's disease patients include decreased acetylcholinesterase and choline acetyl transferase activity, indicating reduced activity of the central cholinergic system, while butyrylcholinesterase (BChE) activity increases. A method that can measure regional BChE activity in the brain in vivo may be useful for investigating the relationship between BChE and Alzheimer's disease. Seven compounds, either piperidinyl or pyrrolidinyl butyrates, were synthesized as BChE substrate radiotracers to map central BChE activity in vivo by positron emission tomography (PET). 14C-labeled compounds were assayed to determine their hydrolysis rates by BChE and the partition coefficient. The five esters of secondary alcohols had lipophilic properties sufficient to pass readily through the blood-brain barrier while the metabolites were sufficiently hydrophilic to be retained in the brain. The esters showed moderate hydrolysis rates by BChE and high specificity for BChE relative to acetylcholinesterase, while two esters of primary alcohols were hydrolyzed too rapidly to estimate reliably the local cerebral BChE activity. From these results, we conclude that one or more of these five esters, when labeled with 11C, would be a useful tracer for quantification of BChE activity by PET. Copyright © 2001 John Wiley & Sons, Ltd.
阿尔茨海默病患者的尸检大脑中的生化变化包括
乙酰胆碱酯酶(AChE)和
胆碱乙酰转移酶(ChAT)活性降低,表明中枢
胆碱能系统活动减少,而丁酰
胆碱酯酶(BChE)活性增加。一种可以在活体中测量大脑区域性BChE活性的方法可能对研究BChE与阿尔茨海默病之间的关系非常有用。合成了七种化合物,分别为
哌啶基或
吡咯烷基
丁酸酯,作为BChE底物放射性示踪剂,通过正电子发射断层扫描(PET)映射中枢BChE活性。用14C标记的化合物进行了测定,以确定它们被BChE
水解的速率和分配系数。这五种第二醇酯具有足够的亲脂性,可以轻松通过血脑屏障,而其代谢物具有足够的亲
水性,可以在大脑中被保留。这些酯被BChE
水解的速率适中,并对BChE相对于
乙酰胆碱酯酶具有较高的特异性,而两种初级醇的酯
水解得过于迅速,无法可靠估计局部大脑BChE活性。根据这些结果,我们得出结论,当这些五种酯中的一种或多种用11C标记时,将是通过PET定量BChE活性的有用示踪剂。版权©2001 John Wiley & Sons, Ltd.