Glucose Transporters And Local Rates Of Cerebral Glucose

葡萄糖转运入脑由促进性转运蛋白（GLUT）介导。在脑中发现三种GLUT亚型：GLUT 1是血脑屏障转运蛋白，GLUT 3是主要的神经元转运蛋白，GLUT 5存在于小胶质细胞中。为了研究葡萄糖利用率和葡萄糖转运蛋白表达变化之间的时间关系，我们研究了Sprague道利大鼠下丘脑-神经垂体系统中水分剥夺的影响。神经垂体含有位于下丘脑视上核和室旁核的神经元的加压素和催产素分泌终末。它还含有神经胶质样垂体细胞，但缺乏BBB。仅在神经叶中发现非血管形式的GLUT 1和GLUT 3，并且在垂体细胞中检测到GLUT 1 mRNA。我们的研究结果表明，3天的水剥夺区域葡萄糖利用率（lCMRglc）增加了15，25，和163%，在室旁核，视上核，和神经叶的垂体，分别。三天的补液使所有三个区域的lCMRglc恢复正常。在神经叶中，在GLUT 1和GLUT 3的45 kDa亚型中也分别观察到28%和43%的增加。再水化3天后，发现GLUT 1浓度正常，但GLUT 3仍升高。再水化7天后进行的测量显示GLUT 3处于对照水平。我们的研究结果表明，在神经激活和恢复的条件下，在lCMRglc和神经垂体中的GLUT 1和GLUT 3的水平的变化是时间相关的，并提高GLUT 1和GLUT 3转运蛋白表达的可能性，可能是由慢性功能活动的变化进行调节。

Glucose transport into brain is mediated by facilitative transporter proteins (GLUT). Three GLUT isoforms are found in brain: GLUT1 is the blood brain barrier transporter, GLUT3 is the predominant neuronal transporter, and GLUT5 is found in microglia. To examine the temporal relationship between alterations in rates of glucose utilization and expression of glucose transporters we studied the effects of water-deprivation in the hypothalamo- neurohypophysial system of Sprague Dawley rats. The neurohypophysis contains vasopressin and oxytocin-secreting terminals of neurons located in the supraoptic and paraventricular nuclei of the hypothalamus. It also contains glial-like pituocytes,but lacks a BBB. Only the nonvascular form of GLUT1 and GLUT3 are found in the neural lobe and GLUT1 mRNA has been detected in pituocytes. Results of our studies show that after 3 days of water deprivation regional rates of glucose utilization (lCMRglc) are increased by 15, 25, and 163% in the paraventricular nuclei, supraoptic nuclei, and neural lobe of the pituitary, respectively. Rehydration for three days restored lCMRglc to normal in all three regions. In the neural lobe increases of 28 and 43% were also observed in the 45 kDa isoform of GLUT1 and GLUT3 respectively. After three days of rehydration normal concentrations of GLUT1 were found, but GLUT3 remained elevated. Measurements made after seven days of rehydration showed GLUT3 at control levels. Our results indicate that, under conditions of neural activation and recovery, changes in lCMRglc and the levels of GLUT1 and GLUT3 in the neurohypophysis are temporally correlated and raise the possibility that GLUT1 and GLUT3 transporter expression may be regulated by chronic changes in functional activity.