Investigation of the Role of Oligopeptide Transporter PEPT1 and Sodium/Glucose Cotransporter SGLT1 in Intestinal Absorption of Their Substrates Using Small GTP-Binding Protein Rab8-Null Mice
Investigation of the Role of Oligopeptide Transporter PEPT1 and Sodium/Glucose Cotransporter SGLT1 in Intestinal Absorption of Their Substrates Using Small GTP-Binding Protein Rab8-Null Mice
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DOI：
10.1124/dmd.108.023689
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发表时间：
2009-03-01
影响因子：
3.9
通讯作者：
Tsuji, Akira
中科院分区：
文献类型：
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作者：
Kato, Yukio;Sugiura, Tomoko;Tsuji, Akira
小GTP结合蛋白Rab 8是寡肽转运蛋白PEPT 1/SLC 15 A1和钠/葡萄糖协同转运蛋白SGLT 1/SLC 5A 1在小肠顶端定位所必需的; Rab 8基因缺陷导致这些转运蛋白的错误定位和表达降低。在此，我们分别使用rab 8基因敲除[rab 8（-/-）]小鼠作为缺乏这些转运蛋白的实验动物，研究了PEPT 1和SGLT 1在β-内酰胺抗生素头孢克肟和α-甲基-d-吡喃葡萄糖苷（α-MDG）胃肠道吸收中的体内作用。在rab 8（-/-）小鼠中口服给药后，头孢克肟和α-MDG的血浆浓度远低于野生型小鼠，而对于安替比林，未观察到口服吸收的这种降低，其膜渗透不是转运蛋白介导的。在存在过量未标记甘氨酰肌氨酸（一种PEPT 1底物）的情况下，通过外翻囊法评估野生型小鼠离体小肠顶侧对头孢克肟的摄取减少。相反，rab 8（-/-）小鼠中的摄取远低于野生型小鼠中的摄取，并且与细胞外标记物甘露醇的摄取相当，这表明rab 8（-/-）小鼠中头孢克肟的顶膜渗透性降低。在野生型小鼠中头孢克肟的摄取是pH依赖性的，在较低的pH值下较高，而在rab 8（-/-）小鼠中在所有检查的pH值下保持在背景水平。这些结果表明，PEPT 1和SGLT 1分别在小鼠体内头孢克肟和α-MDG的胃肠道吸收中发挥重要作用。本研究结果还说明了分选机器蛋白Rab 8的药代动力学影响。
A small GTP-binding protein, Rab8, is essential for apical localization of oligopeptide transporter PEPT1/SLC15A1 and sodium/glucose cotransporter SGLT1/SLC5A1 in small intestine; deficiency of rab8 gene results in mislocalization and reduced expression of these transporters. Here, we examined the role of PEPT1 and SGLT1 in vivo in gastrointestinal absorption of a beta-lactam antibiotic, cefixime, and alpha-methyl-d-glycopyranoside (alpha-MDG), respectively, using rab8 gene knockout [rab8(-/-)] mice as experimental animals deficient in those transporters. Plasma concentration of cefixime and alpha-MDG after oral administration in rab8(-/-) mice was much lower than that in wild- type mice, whereas such reduction in oral absorption was not observed for antipyrine, membrane permeation of which is not transporter-mediated. Uptake of cefixime from the apical side of isolated small intestine assessed by means of the everted sac method in wild- type mice was decreased in the presence of excess unlabeled glycylsarcosine, a PEPT1 substrate. In contrast, the uptake in rab8(-/-) mice was much lower than that in wild- type mice and comparable with that of an extracellular marker, mannitol, suggesting that the apical membrane permeability of cefixime was reduced in rab8(-/-) mice. Uptake of cefixime in wild-type mice was pH-dependent, being higher at lower pH, whereas that in rab8(-/-) mice remained at the background level at all pH values examined. These results suggest that PEPT1 and SGLT1 play an important role in gastrointestinal absorption of cefixime and alpha-MDG, respectively, in vivo in mice. The present findings also illustrate the pharmacokinetic influence of the sorting machinery protein Rab8.