Membrane Permeability and Its Improvement in Intestinal Absorption of Macromolecular Drugs

为了提高多肽等大分子化合物的可吸收性，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，caprate （C10）诱导结阻降低，膜电容增加，FD4K通透性增加，提示C10是一种有效的细胞旁增强剂。钙调素抑制剂W7可抑制C10的作用，提示C10的作用与钙调素依赖性结膜周围肌动球蛋白的收缩有关。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也增加了细胞内Ca^<2+>水平，而W7抑制了这种增加作用，提示Ca^<2+>水平的增加与肌动球蛋白的收缩有关。研究了多肽在Peyer's patches （PP）上的吸收。相比空肠上皮，更多的牛血清白蛋白（BSA）和刀豆蛋白A （ConA）通过PP转运。特别是在PP中，ConA与M细胞膜表面的甘露糖结合位点结合，并通过吸附内吞作用进行转运。当BSA与ConA偶联时，观察到转运增加。目前正在研究包括牛血清白蛋白或ConA在内的pp靶微球的制备。综上所述，本研究通过C10作为细胞旁增强剂和PP作为吸收位点的有效应用，获得了改善大分子化合物肠道吸收的有用信息。

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.