Caillard I, Tomé D
Institut National de la Recherche Agronomique Unité de Nutrition Humaine et Physiologie, Intestinale, Faculté des Sciences Pharmaceutiques et Biologiques, Paris, France.
Am J Physiol. 1994 Jun;266(6 Pt 1):G1053-9. doi: 10.1152/ajpgi.1994.266.6.G1053.
This study was undertaken to investigate the mechanisms of beta-lactoglobulin transport and its regulation in rabbit intestinal mucosa. beta-Lactoglobulin, the major bovine milk whey protein, was slightly degraded by ileal brush-border membranes, indicating the presence of phosphoramidon-insensitive neutral endoproteases. Modulation of 14C-radiolabeled beta-lactoglobulin transport across rabbit ileum mounted in Grass diffusion cells was studied in Ringer solution in the presence and absence of (in mM) 25 glucose, 10 galactose, and 0.5 colchicine. The transport was also measured in Dulbecco's modified Eagle's medium as a more "balanced" medium. The transport of the degraded products and of [3H]polyethylene glycol-4000, which was used as an extracellular marker, was enhanced by addition of glucose, presumably indicating passage through the tight junctions. The transepithelial passage of intact protein was estimated to be 10-20% by trichloroacetic acid precipitation and high-performance liquid chromatography, thus indicating the effective transport of the intact protein. The passage of the intact protein was inhibited by both colchicine, a microtubule-depolymerizing agent, and galactose by 50 and 30%, respectively. Galactose-like glycoconjugates, known to be present on the membrane, might be involved in the interaction between the protein and the brush border.
本研究旨在探讨β-乳球蛋白在兔肠黏膜中的转运机制及其调节。β-乳球蛋白是牛乳清中的主要蛋白质，在回肠刷状缘膜中会轻微降解，这表明存在对磷酰胺不敏感的中性内蛋白酶。在有和没有（以毫摩尔计）25葡萄糖、10半乳糖和0.5秋水仙碱的林格氏溶液中，研究了14C放射性标记的β-乳球蛋白跨安装在格拉斯扩散池中的兔回肠的转运调节。转运也在杜尔贝科改良的伊格尔培养基中进行测量，该培养基是一种更“平衡”的培养基。添加葡萄糖可增强降解产物和用作细胞外标记物的[3H]聚乙二醇-4000的转运，这可能表明其通过紧密连接。通过三氯乙酸沉淀和高效液相色谱法估计完整蛋白质的跨上皮转运为10%-20%，从而表明完整蛋白质的有效转运。完整蛋白质的转运分别被微管解聚剂秋水仙碱和半乳糖抑制了50%和30%。已知存在于膜上的类半乳糖糖缀合物可能参与了蛋白质与刷状缘之间的相互作用。
