In vivo NMR study on the brain metabolism and biological active substabces under anesthesia and hypoxia

用~(13)&gt；C，~(31)&gt；P和~1H核磁共振波谱研究了缺氧和缺血时大鼠脑内葡萄糖代谢及能量状态和生物活性物质的变化。雄性Wistar大鼠用氯胺酮(50-75 mg/kg，ip)麻醉。机械通入30%O2、69.5%N_2和0.5%氟烷的混合气。静脉滴注葡萄糖(250 mg/kg)2次，间隔10min。[1-^；lt；13&gt；C]葡萄糖输注后，[1-^；lt；13&gt；C]葡萄糖在92.7ppm和96.7ppm处出现明显的C_1位插入和异常信号。谷氨酸(Glu)中C2、C3和C4位的信号也分别出现在55、27和34ppm。Glu-C2和Glu-C3信号增强晚于Glu-C4。谷氨酸信号之间的时间滞后可以反映TCA周期的周转速度。在低氧实验中，吸气气体中O_2浓度降至6-7%(93-94%N_2)。低氧时，乳酸-13和C3的信号出现在…超过21ppm并增加，-葡萄糖信号减弱，而-葡萄糖信号保持其强度。葡萄糖和葡萄糖之间信号强度变化的差异表明，在缺氧的大脑中，葡萄糖的消耗量超过了葡萄糖。在相似的低氧条件下，30min内磷酸肌酸(PCr)的信号强度降低了27%，而ATP的信号无明显变化。在~1H谱中，乳酸-CH_3信号的增加也提示缺氧脑中无氧糖酵解的增强。股静脉注射[1-^&lt；13&gt；C]-葡萄糖500 mg/kg。双侧颈总动脉结扎造成大鼠双侧颈总动脉结扎所致脑缺血模型。在缺血脑中，葡萄糖和葡萄糖的信号迅速消失，而乳酸-13和C3的信号变得明显。谷氨酸信号在缺血过程中甚至在缺血后均未出现。在~1t；31&gt；P谱中，PCR和ATP的信号都消失了。因此，脑缺血后不仅有能荷分布，谷氨酸的合成也有分布。较少

The glucose metabolism and the changes in energy state and biological active substances in the brain during hypoxia and ischemia were investigated by ^<13>C, ^<31>P and ^1H NMR spectroscopy. Male Wistar rats were anesthetized with ketamine (50-75mg/kg i.p.) and ventilated mechanically with a mixture of 30% O_2, 69.5% N_2 and 0.5% halothane. [1-^<13>C]glucose (250Mg/kg) was infused twice through femoral vein at 10 min interval. [1-^<13>C]Glucose infusion gave apparent signals of C1 position in - and - anomers of [1-^<13>C]glucose at 92.7 and 96.7 ppm, respectively. Signals of C2, C3 and C4 positions in glutamate (glu) also appeared at 55, 27 and 34 ppm, respectively. The intensity of glu-C2 and glu-C3 signals increased later than that of glu-C4. The time lag between the glu signals may reflect the turnover rate of the TCA cycle. In the hypoxic experiments, O_2 concentration in the inspiratory gas was reduced to 6-7% (93-94% N_2). During hypoxia, the signal of lactate-^<13>C3 appeared at … More 21 ppm and increased, and the -glucose signal diminished, whereas the -glucose signal kept its intensity. The difference in changes of the signal intensity between -and -glucose suggests that -glucose is consumed more than -glucose in the hypoxic brain. Under similar hypoxic condition, the ^<31>P signal intensity of creatine phosphate (pcr) decreased by 27% but the signal of ATP was unchanged in 30min. In the ^1H spectra, increase in the lactate-CH_3 signal also suggests the enhancement of anaerobic glycolisis in hypoxic brain.Mongolian gerbils were anesthetized with pentobarbital (35mg/kg, i.p.). A bolus of [1-^<13>C]-glucose (500mg/kg) was injected into femoral vein. Forbrain ischemia by bilateral common carotid occlusion was induced 15min after the glucose injection. In the ischemic brain, signals of both - and -glucose rapidly disappeared, and the signal of lactate- ^<13>C3 became prominent. The glutamate signals did not appeare during ischemia and even in post-ischemia. In the ^<31>P spectra, signals of both Pcr and ATP disappeared. Thereford, not only energy charge but also glutamate synthesis may be deperssed in the ischemic brain. Less