Dudrick P S, Salloum R M, Copeland E M, Souba W W
Department of Surgery, University of Florida College of Medicine, Gainesville.
J Surg Res. 1992 Apr;52(4):372-7. doi: 10.1016/0022-4804(92)90118-j.
The early effects of endotoxin (4 hr after a single dose of Escherichia coli LPS, 7.5 mg/kg) on L-glutamine (GLN) transport across the jejunal brush border of rats were studied. Jejunal brush border membrane vesicles (BBMVs) were prepared by a Mg2+ aggregation/differential centrifugation technique. Vesicle purity and integrity were confirmed by a 15-fold enrichment of brush border marker enzymes, osmotic activity, transport overshoots in the presence of sodium, and similar 1- and 2-hr equilibrium values. L-[3H]GLN transport in jejunal BBMVs was measured by a millipore filtration technique. Na(+)-dependent glutamine transport, which accounted for greater than 80% of total transport, was increased twofold in BBMVs from endotoxin-treated rats (67 +/- 5 pmole/mg protein/15 sec vs 38 +/- 3, P less than 0.01). Endotoxin treatment did not alter the activity of the Na(+)-independent carrier. Simultaneously, intestinal extraction of glutamine from the bloodstream fell by 56% (15.1 +/- 2.3% in controls vs 6.6 +/- 1.3% in endotoxin-treated rats, P less than 0.01). This reduction in the uptake of circulating glutamine could not be accounted for by a fall in the arterial concentration. Thus, soon after endotoxemia brush border glutamine uptake is increased while consumption of glutamine across the basolateral membrane is decreased. This increased uptake may support protein synthesis and may provide a biochemical rationale for the use of early enteral nutrition after the onset of critical illness.
研究了内毒素（单剂量大肠杆菌脂多糖7.5mg/kg，4小时后）对大鼠空肠刷状缘L-谷氨酰胺（GLN）转运的早期影响。通过Mg2+聚集/差速离心技术制备空肠刷状缘膜囊泡（BBMVs）。通过刷状缘标记酶富集15倍、渗透活性、在钠存在下的转运过冲以及相似的1小时和2小时平衡值来确认囊泡的纯度和完整性。通过微孔过滤技术测量空肠BBMVs中L-[3H]GLN的转运。在内毒素处理大鼠的BBMVs中，占总转运量80%以上的钠依赖性谷氨酰胺转运增加了两倍（67±5pmol/mg蛋白质/15秒对38±3，P<0.01）。内毒素处理未改变非钠依赖性载体的活性。同时，肠道从血液中提取谷氨酰胺的量下降了56%（对照组为15.1±2.3%，内毒素处理大鼠为6.6±1.3%，P<0.01）。循环谷氨酰胺摄取的这种减少不能用动脉浓度的下降来解释。因此，在内毒素血症后不久，刷状缘谷氨酰胺摄取增加，而跨基底外侧膜的谷氨酰胺消耗减少。这种增加的摄取可能支持蛋白质合成，并可能为危重病发作后早期肠内营养的使用提供生化依据。
