ESTIMATES OF MICHAELIS-MENTEN CONSTANTS FOR THE 2 MEMBRANES OF THE BRAIN ENDOTHELIUM
ESTIMATES OF MICHAELIS-MENTEN CONSTANTS FOR THE 2 MEMBRANES OF THE BRAIN ENDOTHELIUM
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DOI：
10.1038/jcbfm.1984.33
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发表时间：
1984-01-01
影响因子：
6.3
通讯作者：
CHRISTENSEN, O
中科院分区：
文献类型：
--
作者：
GJEDDE, A;CHRISTENSEN, O
对血脑屏障易化扩散的示踪研究导致计算描述转运速率的Michaelis-Menten常数。屏障由2个内皮细胞膜组成，单个Michaelis-Menten常数与2个细胞膜的相关性尚不清楚。用公式表示了2个内皮细胞膜的模型，它表明，当跨内皮的转运迅速（Pi > 10-6 cm s-1）时，测得的Michaelis-Menten常数是单个膜性质的简单函数。在示踪剂实验中确定的米氏常数描述了促进扩散在稳态下，只有当2个膜具有相似的传输性能。作为这一观察结果的应用，3个实验研究进行了检查，测量葡萄糖转运的稳态，并表明，从示踪剂实验计算的葡萄糖转运的Michaelis-Menten常数等于从稳态实验计算的常数。脑毛细血管内皮细胞的管腔膜和近管腔膜具有相同的葡萄糖转运特性。
Tracer studies on facilitated diffusion across the blood-brain barrier lead to the calculation of Michaelis-Menten constants that describe the rate of transport. The barrier consists of 2 endothelial cell membranes, and the relevance of single Michaelis-Menten constants in relation to the 2 cell membranes is unknown. A model of 2 endothelial cell membranes was formulated and it shows that the measured Michaelis-Menten constants are simple functions of the properties of the individual membranes when transport across the endothelium is rapid (Pi > 10-6 cm s-1). The Michaelis-Menten constants determined in tracer experiments describe facilitated diffusion in the steady-state only if the 2 membranes have similar transport properties. As an application of this observation, 3 experimental studies were examined that measure glucose transport in the steady-state and show that the Michaelis-Menten constants for glucose transport calculated from the tracer experiments are equal to the constants calculated from the steady-state experiments. The luminal and abluminal membranes of brain capillary endothelial cells have equal glucose transport properties.