Characterization of glutamine transport by liver plasma membrane vesicles.
Characterization of glutamine transport by liver plasma membrane vesicles.
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肝质膜囊泡谷氨酰胺转运的表征。
DOI：
10.1152/ajpendo.1986.251.5.e509
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Barrett,EJ
中科院分区：
文献类型：
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作者：
Jacob,R;Rosenthal,N;Barrett,EJ
从正常和糖尿病大鼠的肝脏中制备了质膜囊泡，并用于表征肝细胞摄取谷氨酰胺的膜转运过程。在正常大鼠囊泡中，当钠离子取代K离子时，谷氨酰胺摄取的初始速度是正常大鼠囊泡的四倍（0.20 +/- 0.02比0.05 +/- 0.02 nmol X mg蛋白-1 X 10 s-1）。在Na+梯度存在的情况下，谷氨酰胺被囊泡摄取是饱和的，Km为1.3 +/- 0.5 mM， Vmax为10 +/- 2.3 nmol X mg-1 X min-1。锂能完全替代Na+刺激谷氨酰胺进入。在施加K+梯度的情况下，谷氨酰胺摄取是其囊外浓度的线性函数。与钠刺激谷氨酰胺的摄取通过钠同调过程发生一致，我们观察到谷氨酰胺刺激22Na+进入囊泡的初始速率提高了4到5倍。我们进一步观察到，当亲脂阴离子在孵育缓冲液中伴随钠时，谷氨酰胺进入更快，这表明Na+-谷氨酰胺通量是电致的。用谷氨酰胺预先加载囊泡并不影响随后标记谷氨酰胺的进入（无交叉刺激），而囊泡内的丙氨酸确实增强了谷氨酰胺的进入，但没有增强谷氨酰胺的进入。四氧嘧啶糖尿病，已知会刺激这些囊泡中的Na+-丙氨酸共转运蛋白，但在任何浓度的测试中都不会增加谷氨酰胺的进入。（摘要删节250字）
Plasma membrane vesicles were prepared from livers of fed normal and diabetic rats and used to characterize the membrane transport process responsible for glutamine uptake by the liver cell. In vesicles from normal rats the initial velocity of glutamine uptake was fourfold more rapid (0.20 +/- 0.02 vs. 0.05 +/- 0.02 nmol X mg protein-1 X 10 s-1) when Na+ replaced K+ in the extravesicular buffer. In the presence of a Na+-gradient glutamine uptake by vesicles was saturable, with a Km of 1.3 +/- 0.5 mM and a Vmax of 10 +/- 2.3 nmol X mg-1 X min-1. Lithium could fully substitute for Na+ in stimulating glutamine entry. In the presence of an imposed K+-gradient glutamine uptake was a linear function of its extravesicular concentration. In accord with the sodium-stimulated uptake of glutamine occurring via a sodium symport process, we observed that glutamine stimulated the initial rate of 22Na+ entry into vesicles by four- to fivefold. We further observed that glutamine entry was more rapid when lipophilic anions accompanied sodium in the incubation buffer, suggesting that Na+-glutamine flux is electrogenic. Preloading of vesicles with glutamine did not effect subsequent entry of labeled glutamine (no transstimulation), whereas intravesicular alanine did enhance alanine but not glutamine entry. Alloxan diabetes, which is known to stimulate the Na+-alanine cotransporter in these vesicles did not increase glutamine entry at any concentration tested.(ABSTRACT TRUNCATED AT 250 WORDS)