AN OLIGOPEPTIDE PERMEATES INTESTINAL TIGHT JUNCTIONS AT GLUCOSE-ELICITED DILATATIONS - IMPLICATIONS FOR OLIGOPEPTIDE ABSORPTION
AN OLIGOPEPTIDE PERMEATES INTESTINAL TIGHT JUNCTIONS AT GLUCOSE-ELICITED DILATATIONS - IMPLICATIONS FOR OLIGOPEPTIDE ABSORPTION
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DOI：
10.1016/0016-5085(91)80016-3
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发表时间：
1991-03-01
期刊：
影响因子：
29.4
通讯作者：
MADARA, JL
中科院分区：
文献类型：
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作者：
ATISOOK, K;MADARA, JL
肠吸收细胞顶膜中Na+-葡萄糖共转运蛋白的转换引起紧密连接结构的改变，包括出现结内扩张。与这些结构反应平行，上皮对离子和营养物大小的溶质的渗透性增加。然而，目前尚不清楚这些观察到的通透性变化与葡萄糖引起的结构改变之间的具体关系。使用血共轭肽示踪剂（MP-11; mol wt,≈1900），本研究表明葡萄糖引起的紧密连接扩张是连接渗透的特定解剖部位。这种肽示踪剂选择性地穿透扩张部位的紧密连接，并在细胞旁间隙局部检测到。当葡萄糖不存在时，同样的示踪剂不会穿透连接。葡萄糖暴露和未暴露的组织都排除了一种血共轭大分子（辣根过氧化物酶；mol wt,≈40,000）。本研究结果表明，在Na+ -葡萄糖激活吸收过程中，小肽的细胞旁通路受到调节。据推测，细胞旁途径可能有助于已知发生的与膳食相关的寡肽吸收，并且以前完全归因于跨细胞途径。
Turnover of the Na+-glucose cotransporter in the apical membrane of intestinal absorptive cells elicits alterations in tight-junction structure including the appearance of intrajunctional dilatations. Paralleling these structural responses, epithelial permeability to ions and nutrient-sized solutes increases. However, it is not known how these observed permeability changes specifically relate to the structural alterations elicited by glucose. Using a hemeconjugated peptide tracer (MP-11; mol wt, ≈ 1900), the present study shows that the glucose-elicited tight-junction dilatations are specific anatomical sites of junctional permeation. This peptide tracer penetrates tight junctions selectively at sites of dilatations and is detected focally within the paracellular space. This same tracer does not penetrate junctions when glucose is not present. A hemeconjugated macromolecule (horseradish peroxidase; mol wt, ≈ 40,000) is excluded by both glucose-exposed and glucose-unexposed tissues. The results of this study show a paracellular pathway for small peptides that is regulated during Na+—glucose-activated absorption. It is speculated that the paracellular pathway may contribute to the meal-related oligopeptide absorption that is known to occur and has previously been wholly attributed to the transcellular route.