Membrane Permeability and Its Improvement in Intestinal Absorption of Macromolecular Drugs

为了提高大分子化合物如多肽的吸收性，研究了吸收促进剂对细胞旁转运的增强作用。在大鼠空肠和结肠中，癸酸盐（C10）诱导连接电阻降低和膜电容增加，并增加FD 4K通透性，表明C10是一种有效的细胞旁增强剂。C10效应被钙调蛋白抑制剂W7抑制，表明该效应与连接周围肌动球蛋白的钙调蛋白依赖性收缩有关。在人结肠癌细胞系（Caco-2）中也观察到上述作用。在Caco-2细胞中，C10也能增加细胞内Ca^<2+>水平，而W7则抑制这种增加作用，表明Ca^<2+>水平的增加与肌动球蛋白的收缩有关。检查肽穿过派尔集合淋巴结（PP）的吸收。牛血清白蛋白（BSA）和刀豆球蛋白A（ConA）通过PP比空肠上皮运输更多。特别是ConA可能与M细胞膜表面的甘露糖结合位点结合，通过吸附胞吞转运。当BSA与ConA缀合时，观察到转运增加。因此，本研究以C10为细胞旁促进剂，以PP为吸收位点，有效地促进了大分子化合物在肠道的吸收，为大分子化合物在肠道的吸收提供了有益的信息。

To improve the absorbability of macromolecular compounds such as polypeptides, enhancement of the paracellular transport by absorption enhancer was examined. In rat jejunum and colon, caprate (C10) induced reduction of junctional resistance and increase in menmbrane capacitance, and increased FD4K permeability, indicating C10 to be an effective paracellular enhancer. The C10 effect was inhibited by calmodulin inhibitor W7, suggesting that the effect relates to calmodulin-dependent contraction of perijunctional actomyosin. The above effects were also observed in human colon carcinoma cell lines (Caco-2). In Caco-2 cells, C10 also increased the intracellular Ca^<2+> level and W7 suppressed the increasing effect, suggesting that increase in Ca^<2+> level relates to contraction of actomyosin. Absorption of peptides across Peyer's patches (PP) was examined. More bovine serum albumin (BSA) and concanavalin A (ConA) were transported across PP than jejunal epithelium. Especially, ConA was suggested to bind to mannose binding sites on membrane surface of M cell in PP and then tranported by adsorptive endocytosis. When BSA is conjugated with ConA, the transport was observed to be increased. Preparation of PP-target microspheres including BSA or ConA is now under investigation.In summary, in this study, useful information on the improvement of intestinal absorption of macromolecule compounds was obtained from effective application of C10 as theparacellular enhancer and PP as the absorption site.