Characterization of L-leucine transport system in brush border membranes from human and rabbit small intestine.
Characterization of L-leucine transport system in brush border membranes from human and rabbit small intestine.
复制标题
人和兔小肠刷状缘膜中 L-亮氨酸转运系统的表征。
DOI：
10.1016/s0026-0495(99)90155-5
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Sax,HC
中科院分区：
文献类型：
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作者：
Iannoli,P;Miller,JH;Wang,HT;Bode,B;Souba,WW;Avissar,NE;Sax,HC
支链氨基酸（BCAAs）亮氨酸、异亮氨酸和缬氨酸通过改善肝脏蛋白质合成和氮经济性对分解代谢患者有益，但其从肠腔的转运尚不明确。采用刷状边界膜泡（BBMV）模型对人和家兔小肠亮氨酸转运系统进行了表征。测定了钠和pH的依赖性以及沿小肠纵轴的运输活性。确定了转运动力学和抑制谱。尽管先前在其他组织中的研究表明亮氨酸运输主要是Na+不依赖的过程，但我们的研究表明亮氨酸运输主要是Na+依赖的过程，主要通过一个类似于肠道系统b0的可饱和ph不依赖转运体发生。该系统b0转运蛋白具有立体异构体特异性。在家兔中也有少量的不依赖Na+的转运成分（<6%）。兔和人对亮氨酸的摄取明显大于对其他临床相关营养素（如谷氨酰胺）的摄取。在家兔中，回肠亮氨酸转运显著大于空肠摄取。虽然人类和家兔转运体的亲和力相似，但家兔转运体具有更大的运载能力（最大转运速度[Vmax]）。这些结果提示亮氨酸在肠黏膜的转运与在其他组织中的转运有显著的不同。
The branched-chain amino acids (BCAAs) leucine, isoleucine, and valine are beneficial to catabolic patients by improving hepatic protein synthesis and nitrogen economy, yet their transport from the intestinal lumen is not well-defined. The leucine transport system in human and rabbit small intestine was characterized using a brush border membrane vesicle (BBMV) model. Sodium and pH dependence and transport activity along the longitudinal axis of the small bowel were determined. Transport kinetics and inhibition profiles were defined. Although previous studies in other tissues show leucine transport to be mostly a Na+-independent process, our studies show that leucine transport is a predominantly Na+-dependent process occurring mainly via a single saturable pH-independent transporter resembling systems B0in the intestine. This system B0transporter demonstrates stereoisomeric specificity. There is also a minor Na+-independent transport component (<6% in rabbits). Leucine uptake in both rabbits and human is significantly greater than the uptake of other clinically relevant nutrients such as glutamine. In the rabbit, ileal leucine transport is significantly greater than jejunal uptake. While the affinities of the human and rabbit transporters are similar, the rabbit transporter has greater carrier capacity (maximal transport velocity [Vmax]). These findings suggest that the transport of leucine in the gut mucosa is significantly different from the transport in other tissues.