Snead O C, Furner R, Liu C C
Department of Pediatrics, University of Alabama, School of Medicine, Birmingham.
Biochem Pharmacol. 1989 Dec 15;38(24):4375-80. doi: 10.1016/0006-2952(89)90645-x.
The formation of 4-[1,4-13C]hydroxybutyric acid ([13C]gamma-hydroxybutyric acid; [13C]GHB) in rat brain was studied following intracerebroventricular (i.c.v.) administration of either 4-[1,4-13C]aminobutyric acid ([13C]GABA or 1,4-[1,4-13C]butanediol ([13C]1,4-BD) to awake, freely moving animals. GHB and [13C]GHB were measured with a gas chromatographic mass spectrometric (GC/MS) technique designed to detect the lactone derivative of GHB with the acid or lactone being determined by conditions of tissue extraction. [13C]GHB was detected following i.c.v. administration of [13C]GABA with a turnover rate of 2.04 nmol/g tissue/hr and [13C]1,4-BD with a turnover rate of 1.4 nmol/g/hr. The formation of [13C]GHB from [13C]GABA was blocked by an inhibitor of GABA-transaminase, but this drug had no effect on the formation of [13C]GHB from [13C]1,4-BD. The latter pathway was also unaffected by alcohol dehydrogenase inhibitors, compounds which block this pathway in the periphery. Further, in the course of these experiments, naturally occurring endogenous gamma-butyrolactone (GBL) was detected in rat brain in a concentration of 200 pmol/g tissue weight, but lactonization in vivo of [13C]GHB formed from either labeled GABA or 1,4-BD was not demonstrated. These data confirm two separate pathways of synthesis for GHB in brain, demonstrate the presence of GBL in brain, and illustrate the utility of a new GC/MS technique for analysis of GHB and for GBL which does not involve extensive derivatization.
在清醒、自由活动的动物脑室内（i.c.v.）注射4-[1,4-¹³C]氨基丁酸（[¹³C]GABA）或1,4-[1,4-¹³C]丁二醇（[¹³C]1,4-BD）后，研究了大鼠脑中4-[1,4-¹³C]羟基丁酸（[¹³C]γ-羟基丁酸；[¹³C]GHB）的形成。使用气相色谱-质谱联用（GC/MS）技术测量GHB和[¹³C]GHB，该技术旨在检测GHB的内酯衍生物，酸或内酯由组织提取条件决定。在脑室内注射[¹³C]GABA后检测到[¹³C]GHB，转换率为2.04 nmol/g组织/小时，注射[¹³C]1,4-BD后转换率为1.4 nmol/g/小时。[¹³C]GABA形成[¹³C]GHB的过程被GABA转氨酶抑制剂阻断，但该药物对[¹³C]1,4-BD形成[¹³C]GHB没有影响。后一种途径也不受乙醇脱氢酶抑制剂的影响，这些化合物在外周阻断该途径。此外，在这些实验过程中，在大鼠脑中检测到天然存在的内源性γ-丁内酯（GBL），浓度为200 pmol/g组织重量，但未证明由标记的GABA或1,4-BD形成的[¹³C]GHB在体内发生内酯化。这些数据证实了脑中GHB的两种独立合成途径，证明了脑中GBL的存在，并说明了一种新的GC/MS技术在分析GHB和GBL方面的实用性，该技术无需广泛衍生化。
