INTESTINAL-ABSORPTION AND EXCRETION OF OCTAPEPTIDES COMPOSED OF D-AMINO-ACIDS
INTESTINAL-ABSORPTION AND EXCRETION OF OCTAPEPTIDES COMPOSED OF D-AMINO-ACIDS
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DOI：
10.1073/pnas.91.5.1942
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发表时间：
1994-03-01
影响因子：
11.1
通讯作者：
MAGGIO, JE
中科院分区：
文献类型：
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作者：
PAPPENHEIMER, JR;DAHL, CE;MAGGIO, JE
正常大鼠饮用含有0.1-25 mg/dl的I-125标记肽的5%葡萄糖/1%肌酸酐，由D氨基酸合成的八肽从肠吸收并经尿排泄。在夜间进食期间，大鼠以约20 ml/hr的速率摄入液体，并以15 ml/hr的速率产生尿液，持续数小时。61 +/- 4%的摄入肌酐和50 +/- 3%的脂不溶性D八肽（EASASYSA，784 Da）通过尿液完整排泄。肌酐的稳态摩尔吸收排泄率等于或超过载体介导的葡萄糖肠道转运的最大速率，这表明肌酐和D八肽都是由溶剂拖曳通过吸收性细胞连接被葡萄糖扩张的细胞旁转运的。超过70%的摄入的葡萄糖也被细胞旁吸收。结果表明，完整的寡肽可以有效地从肠道吸收时，他们不被膜结合的肽酶的刷状缘水解。这些结果也为最近的理论提供了支持，该理论提出膜消化与细胞旁溶剂阻力的耦合占正常肠道吸收营养物质的主要部分。
Octapeptides synthesized from D amino acids were absorbed from the intestine and excreted in urine of normal rats drinking 5% glucose/1% creatinine containing the I-125-labeled peptides at 0.1-25 mg/dl. The rats ingested fluid at the rate of about 20 ml/hr and produced urine at 15 ml/hr for several hours during the nocturnal feeding period. Sixty-one +/- 4% of the ingested creatinine and 50 +/- 3% of a lipid-insoluble D octapeptide (EASASYSA, 784 Da) were excreted intact in the urine. The steady-state molar rate of absorption-excretion of creatinine equaled or exceeded the maximum rate of carrier-mediated intestinal transport of glucose, suggesting that both the creatinine and the D octapeptide were transported paracellularly by solvent drag through absorptive cell junctions that were dilated by the glucose. More than 70% of the ingested glucose was also absorbed paracellularly. The results demonstrate that intact oligopeptides can be absorbed efficiently from the intestine when they are not hydrolyzed by membrane-bound peptidases of the brush border. The results also provide support for recent theories proposing that coupling of membrane digestion with paracellular solvent drag accounts for a major fraction of normal intestinal absorption of nutrients.