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首页> 外文期刊>American Journal of Physiology >Expression of apical membrane L-glutamate transporters in neonatal porcine epithelial cells along the small intestinal crypt-villus axis.
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Expression of apical membrane L-glutamate transporters in neonatal porcine epithelial cells along the small intestinal crypt-villus axis.

机译：沿小肠隐窝-绒毛轴的新生猪上皮细胞中顶膜L-谷氨酸转运蛋白的表达。

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摘要

Enteral l-glutamate is extensively utilized as an oxidative fuel by the gut mucosa in the neonate. To identify major uptake pathways and to understand uptake regulation, we examined transport kinetics and molecular identities of apical membrane l-glutamate transporters in epithelial cells sequentially isolated along the small intestinal crypt-villus axis from milk protein-fed, 16-day-old pigs. The distended intestinal sac method was used to isolate 12 sequential cell fractions from the tip villus to the bottom crypt. Initial rates and kinetics of l-glutamate uptake were measured with l-[G-(3)H]glutamate by fast filtration in apical membrane vesicles prepared by Mg(2+) precipitation and differential centrifugation, with membrane potential clamped by SCN(-). Initial l-glutamate uptake results suggested the presence of B(o) and X(AG)(-) transport systems, but the X(AG)(-) system was predominant for uptake across the apical membrane. Kinetic data suggested that l-glutamate uptake through the X(AG)(-) system was associated with higher maximal transport activity but lower transporter affinity in crypt than in villus cells. Molecular identity of the X(AG)(-) glutamate transporter, based on immunoblot and RT-PCR analysis, was primarily the defined excitatory amino acid carrier (EAAC)-1. EAAC-1 expression was increased with cell differentiation and regulated at transcription and translation levels from crypt to upper villus cells. In conclusion, efficiency and capacity of luminal l-glutamate uptake across the apical membrane are regulated by changing expression of the X(AG)(-) system transporter gene EAAC-1 at transcription and translation levels as well as maximal uptake activity and transporter affinity along the intestinal crypt-villus axis in the neonate.
机译：新生儿肠粘膜广泛使用肠内l-谷氨酸作为氧化燃料。为了确定主要的摄取途径并了解摄取调节，我们研究了从乳汁喂养的16日龄小猪沿小肠隐窝-绒毛轴顺序分离的上皮细胞中顶膜l-谷氨酸转运蛋白的转运动力学和分子特性。 。扩张的肠囊法用于分离从绒毛到底部隐窝的12个连续的细胞级分。通过快速过滤在由Mg（2+）沉淀和差速离心制备的心尖膜囊泡中用L- [G-（3）H]谷氨酸测定L-谷氨酸摄取的初始速率和动力学，膜电位被SCN（- ）。最初的L-谷氨酸摄取结果表明存在B（o）和X（AG）（-）转运系统，但X（AG）（-）系统主要通过顶膜吸收。动力学数据表明，相比于绒毛细胞，通过X（AG）（-）系统吸收的谷氨酸与更高的最大转运活性有关，但与隐窝细胞的转运亲和力较低有关。 X（AG）（-）谷氨酸转运蛋白的分子身份，基于免疫印迹和RT-PCR分析，主要是定义的兴奋性氨基酸载体（EAAC）-1。 EAAC-1表达随着细胞分化而增加，并在从隐窝到上层绒毛细胞的转录和翻译水平受到调节。总之，通过改变转录和翻译水平的X（AG）（-）系统转运蛋白基因EAAC-1的表达以及最大吸收活性和转运蛋白亲和力，可以调节L-谷氨酸在根尖膜上吸收的效率和能力。沿肠道隐窝-绒毛轴。

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