Irie Megumi, Terada Tomohiro, Tsuda Masahiro, Katsura Toshiya, Inui Ken-Ichi
Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Sakyo-ku, 606-8507, Kyoto, Japan.
Pflugers Arch. 2006 Apr;452(1):64-70. doi: 10.1007/s00424-005-0005-x. Epub 2005 Nov 10.
H(+)-coupled peptide transporter 1 (PEPT1) and the basolateral peptide transporter mediate the absorption of small peptides and peptide-like drugs in the small intestine. Recently, we constructed a mathematical model to simulate glycylsarcosine (Gly-Sar) transport in Caco-2 cells. In this study, we attempted to adjust our model to a change in the expression level of PEPT1. To obtain cell lines expressing PEPT1 at different levels, recloning of Caco-2 cells was performed, and nine clones were isolated. Compared with parental cells, clones 1 and 9 exhibited the lowest and the highest levels of [(14)C]Gly-Sar uptake from the apical side, respectively, whereas activities of the basolateral peptide transporter were comparable. Kinetic analysis demonstrated that the difference in the activity of PEPT1 was accounted by variations in V (max). Moreover, PEPT1 mRNA level was positively related to the activity of [(14)C]Gly-Sar uptake (r=0.55). Based on these findings, the V (max) value of PEPT1 was defined as a variable using the amount of PEPT1 mRNA as an index of the expression level. With this improved model, Gly-Sar transport in clones 1 and 9 was well-predicted, suggesting that our model can simulate Gly-Sar transport in cells expressing PEPT1 at different levels.
H(+)-偶联肽转运体1（PEPT1）和基底外侧肽转运体介导小肠中小肽和类肽药物的吸收。最近，我们构建了一个数学模型来模拟甘氨酰肌氨酸（Gly-Sar）在Caco-2细胞中的转运。在本研究中，我们试图使我们的模型适应PEPT1表达水平的变化。为了获得不同水平表达PEPT1的细胞系，对Caco-2细胞进行了再克隆，并分离出9个克隆。与亲代细胞相比，克隆1和克隆9分别表现出从顶端摄取[(14)C]Gly-Sar的最低和最高水平，而基底外侧肽转运体的活性相当。动力学分析表明，PEPT1活性的差异是由V（max）的变化引起的。此外，PEPT1 mRNA水平与[(14)C]Gly-Sar摄取活性呈正相关（r = 0.55）。基于这些发现，以PEPT1 mRNA量作为表达水平指标，将PEPT1的V（max）值定义为一个变量。利用这个改进的模型，克隆1和克隆9中的Gly-Sar转运得到了很好的预测，这表明我们的模型可以模拟不同水平表达PEPT1的细胞中的Gly-Sar转运。
