Neutral amino acid transport by the blood-brain barrier. Membrane vesicle studies.
Neutral amino acid transport by the blood-brain barrier. Membrane vesicle studies.
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DOI：
10.1016/s0021-9258(18)35701-6
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发表时间：
1992-12
期刊：
影响因子：
--
通讯作者：
M. S. D. Pino;R. Hawkins;D. Peterson
中科院分区：
文献类型：
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作者：
M. S. D. Pino;R. Hawkins;D. Peterson
内皮细胞膜是血脑屏障的所在地，是从牛脑的毛细血管中获得的。通过在不连续Ficoll梯度上离心分离腔膜和近腔膜。电子显微镜显示膜制剂几乎完全由密封的囊泡组成。潜在酶活性的释放表明两种膜制剂基本上都是正面朝外的。管腔囊泡对放射性标记的 L-苯丙氨酸的摄取与膜蛋白浓度成正比，结合率低于 10%。运输是通过高亲和力载体（Km 11.8 +/- 0.1 microM，渐近标准误差）进行的，该载体几乎没有或没有立体特异性，并且与 Na+ 或 H+ 梯度无关。 L-色氨酸、L-亮氨酸、2-氨基双环[2,2,1]庚烷-2-甲酸和D-苯丙氨酸抑制转运，但N-(甲基氨基)-异丁酸不抑制转运。 Abluminal 膜显示出一种额外的成分，其中 Na+ 梯度加速了苯丙氨酸和 N-(甲基氨基)-异丁酸的转运。这些研究证明了膜囊泡作为模型来表征形成血脑屏障的极性内皮细胞的不同膜的运输特性的效用。
Endothelial cell membranes, the site of the blood-brain barrier, were obtained from the capillaries of cow brain. The luminal and abluminal membranes were separated by centrifugation on a discontinuous Ficoll gradient. Electron microscopy revealed that the membrane preparations consisted almost entirely of sealed vesicles. The release of latent enzyme activity showed that both membrane preparations were primarily right side out. Radiolabeled L-phenylalanine uptake by luminal vesicles was proportional to membrane protein concentration, with less than 10% binding. Transport was by a high affinity carrier (Km 11.8 +/- 0.1 microM, asymptotic standard error) that showed little or no stereospecificity, and was independent of Na+ or H+ gradients. Transport was inhibited by L-tryptophan, L-leucine, 2-aminobicyclo[2,2,1]heptane-2-carboxylate and D-phenylalanine, but not by N-(methylamino)-isobutyrate. Abluminal membranes showed an additional component in which a Na+ gradient accelerated the transport of both phenylalanine and N-(methylamino)-isobutyrate. These studies demonstrate the utility of membrane vesicles as a model to characterize the transport properties of the distinct membranes of the polar endothelial cells that form the blood-brain barrier.