Changes of plasma glutamine concentration and hepatocyte membrane system N transporters expression in early endotoxemia.
Changes of plasma glutamine concentration and hepatocyte membrane system N transporters expression in early endotoxemia.
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DOI：
10.1016/j.jss.2009.08.027
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发表时间：
2011-04
期刊：
影响因子：
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通讯作者：
Wei-ya Wang;Yousheng Li;Wenbo Zhang;Feng Zhang;Jie‐shou Li
中科院分区：
文献类型：
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作者：
Wei-ya Wang;Yousheng Li;Wenbo Zhang;Feng Zhang;Jie‐shou Li
背景谷氨酰胺在健康和危重疾病中发挥着重要作用。在内毒素血症期间，谷氨酰胺代谢，包括其血浆水平和转运，发生显着变化。先前的研究表明，肝细胞中的系统N转运蛋白在肝脏谷氨酰胺转运中发挥着重要作用。然而，人们对肝细胞质膜中N系统转运蛋白mRNA和蛋白表达的变化知之甚少。此外，内毒素血症期间血浆谷氨酰胺浓度的变化仍然存在争议。本研究通过腹腔注射脂多糖(LPS)观察早期内毒素血症大鼠的变化。材料与方法腹腔注射3、6、12mg/kg体重剂量的LPS建立内毒素血症大鼠模型。以等体积0.9%生理盐水作为对照。注射前及注射后2、4、6、12、24小时，分别采用高效液相色谱、实时PCR、Western blot检测血浆谷氨酰胺浓度、肝细胞质膜SNAT3和SNAT5转运蛋白的mRNA和蛋白表达。 结果注射LPS后4～12h（3mg/kg）和2～6h（6mg/kg， 12mg/kg)注射后与其生理水平相比，24h时6、12mg/kg组显着下降。 LPS以时间和剂量依赖性方式增强SNAT3和SNAT5的mRNA和蛋白表达。结论内毒素血症大鼠血浆谷氨酰胺浓度在内毒素血症早期短暂升高，但随后随时间推移逐渐降低。 LPS对系统N表达的影响不仅发生在蛋白质水平，还发生在mRNA水平。败血症或内毒素血症患者在发病后6～12小时开始补充谷氨酰胺是合理的。
BACKGROUNDGlutamine plays important roles in health and critical illness. During endotoxemia, glutamine metabolism, including its plasma level and transport, changes markedly. Previous studies have demonstrated that system N transporters in hepatocytes play a major role in hepatic glutamine transport. However, little is known about the changes of mRNA and protein expression of system N transporters in hepatocyte plasma membrane. Furthermore, the alteration of plasma glutamine concentration during endotoxemia is still controversial. In this study, we investigated the changes in early endotoxemic rats by intraperitoneal injection of lipopolysaccharide (LPS).MATERIALS AND METHODSThree, 6, 12mg/kg body weight doses of LPS were injected intraperitoneally to establish the endotoxemic rat model; equal volume of 0.9% saline was used as the control. Before and 2, 4, 6, 12, 24h after injections, plasma glutamine concentration, mRNA, and protein expression of SNAT3 and SNAT5 transporters in hepatocyte plasma membrane were detected by high performance liquid chromatography, real-time PCR, and Western blot, respectively.RESULTSLPS injection resulted in a marked increase of the plasma glutamine concentration from 4 to 12h (3mg/kg) and 2 to 6h (6mg/kg, 12mg/kg) after the injection compared with its physiologic level, and a significant decrease in 6, 12mg/kg groups at 24h. Both the mRNA and protein expression of SNAT3 and SNAT5 were enhanced by LPS in a time- and dose-dependent manner.CONCLUSIONSThe plasma glutamine concentration in endotoxemic rat increased transiently during early endotoxemia but subsequently decreased over time. The effect of LPS on system N expression occurs not only at the protein level, but also at the mRNA level. It is reasonable to supplement glutamine for patients with sepsis or endotoxemia begin at 6 to 12h after the development of disease.