Study on analytical toxicologic evaluation of endogenous γ-hydroxybutyric acid levels in postmortem body fluids

用顶空气相色谱法测定了25例无腐败或轻度腐败的尸检标本的各种体液中内源性γ-羟丁酸（GHB）的含量。股静脉血GHB含量（4.6±3.4μg/ml，n=23）明显高于脑脊液（1.8±1.5μg/ml，n=9）、玻璃体液（0.9±1.7μg/ml，n=8）、胆汁（1.0±1.1μg/ml，n=9）和尿液（0.6±1.2μg/ml，n=12）。从不同地点采集的血液样本中的伽马-羟丁酸水平相似。血液和尿液中GHB的检测限分别为30 μg/ml和10μg/ml，可用于区分无腐败或几乎无腐败的死者体内的外源性和内源性GHB。采用液-液萃取-气相色谱法测定了20名健康志愿者尿样中GHB的含量。平均饮酒者（男性）4人，平均吸烟者（男性）4人，非吸烟者/非饮酒者12人（男性7人，女性5人）。男性尿GHB含量吸烟者（0.52±0.37μg/ml）高于不吸烟/不饮酒者（0.28±0.21μg/ml）和饮酒者（0.23±0.04μg/ml）。家兔皮下注射乙醇2 g/kg、尼古丁3 mg/kg、盐酸甲基苯丙胺5 mg/kg、盐酸可卡因5 mg/kg、盐酸吗啡5 mg/kg或异戊巴比妥钠5 mg/kg，每日1次，连续5 d，血液中内源性GHB水平无明显变化。短期服用这些滥用药物可能不会影响伽马--羟丁酸的内源性产生。

Endogenous γ-hydroxybutyric acid (GHB) levels in various postmortem fluid samples of 25 autopsy cases with no or little putrefaction were measured by headspace gas chromatography after GHB was converted to γ-butyrolactone. Endogenous GHB levels were significantly higher in femoral venous blood (4.6±3.4μg/ml, n=23) than in cerebrospinal fluid (1.8±1.5μg/ml, n=9), vitreous humor (0.9±1.7μg/ml, n=8), bile (1.0±1.1μg/ml, n=9) and urine (0.6±1.2μg/ml, n=12). GHB levels were similar in blood samples taken from different sites. Cut-off limits of 30 and 10μg/ml can be proposed for blood and urine, respectively, to discriminate between exogenous and endogenous GHB in decedents showing no or little putrefaction.We have devised a simple method for detecting GHB in blood and urine by gas chromatography and liquid-liquid extraction with a back-extraction step for purification. The sensitivity of this method was approximately three times as high as that of the headspace gas chromatographic method.Endogenous levels of GHB in urine samples obtained from 20 healthy volunteers were measured by gas chromatography combined with liquid-liquid extraction. There were 4 average drinkers (males), 4 average smokers (males), and 12 nonsmokers/nondrinkers (7 males and 5 females). The urinary levels of GHB in males were higher in smokers (0.52±0.37μg/ml) than in nonsmokers/nondrinkers (0.28±0.21μg/ml) and drinkers (0.23±0.04μg/ml). No gender differences were observed in the urinary levels of endogenous GHB.When 2 g/kg of ethanol, 3 mg/kg of nicotine, 5 mg/kg of methamphetamine hydrochloride, 5 mg/kg of cocaine hydrochloride, 5 mg/kg of morphine hydrochloride, or 5 mg/kg of sodium amobarbital was subcutaneously administered to rabbits once a day for 5 days, no changes in endogenous GHB levels in blood were observed. Short term administration of those drugs of abuse may not affect endogenous production of GHB.