Abbot Emily L, Grenade Danielle S, Kennedy David J, Gatfield Kelly M, Thwaites David T
Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH.
Br J Pharmacol. 2006 Feb;147(3):298-306. doi: 10.1038/sj.bjp.0706557.
The aim of this investigation was to determine if the human proton-coupled amino-acid transporter 1 (hPAT1 or SLC36A1) is responsible for the intestinal uptake of the orally-administered antiepileptic agent 4-amino-5-hexanoic acid (vigabatrin). The Caco-2 cell line was used as a model of the human small intestinal epithelium. Competition experiments demonstrate that [3H]GABA uptake across the apical membrane was inhibited by vigabatrin and the GABA analogues trans-4-aminocrotonic acid (TACA) and guvacine, whereas 1-(aminomethyl)cyclohexaneacetic acid (gabapentin) had no affect. Experiments with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF)-loaded Caco-2 cells demonstrate that apical exposure to vigabatrin and TACA induce comparable levels of intracellular acidification (due to H+/amino-acid symport) to that generated by GABA, suggesting that they are substrates for a H+ -coupled absorptive transporter such as hPAT1. In hPAT1 and mPAT1-expressing Xenopus laevis oocytes [3H]GABA uptake was inhibited by vigabatrin, TACA and guvacine, whereas gabapentin failed to inhibit [3H]GABA uptake. In Na+ -free conditions, vigabatrin and TACA evoked similar current responses (due to H+/amino-acid symport) in hPAT1-expressing oocytes under voltage-clamp conditions to that induced by GABA (whereas no current was observed in water-injected oocytes) consistent with the ability of these GABA analogues to inhibit [3H]GABA uptake. This study demonstrates that hPAT1 is the carrier responsible for the uptake of vigabatrin across the brush-border membrane of the small intestine and emphasises the therapeutic potential of hPAT1 as a delivery route for orally administered, clinically significant GABA-related compounds.
本研究的目的是确定人类质子偶联氨基酸转运体1（hPAT1或SLC36A1）是否负责口服抗癫痫药物4-氨基-5-己酸（vigabatrin）的肠道吸收。Caco-2细胞系被用作人类小肠上皮的模型。竞争实验表明，vigabatrin以及GABA类似物反式-4-氨基巴豆酸（TACA）和胍基乙酸可抑制[3H]GABA跨顶端膜的摄取，而1-(氨甲基)环己烷乙酸（加巴喷丁）则无影响。对装载了2',7'-双(2-羧乙基)-5(6)-羧基荧光素（BCECF）的Caco-2细胞进行的实验表明，顶端暴露于vigabatrin和TACA会诱导与GABA产生的细胞内酸化水平相当（由于H+/氨基酸同向转运），这表明它们是H+偶联吸收转运体（如hPAT1）的底物。在表达hPAT1和mPAT1的非洲爪蟾卵母细胞中，vigabatrin、TACA和胍基乙酸可抑制[3H]GABA的摄取，而加巴喷丁未能抑制[3H]GABA的摄取。在无Na+条件下，vigabatrin和TACA在电压钳制条件下在表达hPAT1的卵母细胞中引发了与GABA诱导的类似电流反应（由于H+/氨基酸同向转运）（而在注射水的卵母细胞中未观察到电流），这与这些GABA类似物抑制[3H]GABA摄取的能力一致。本研究表明，hPAT1是负责vigabatrin跨小肠刷状缘膜摄取的载体，并强调了hPAT1作为口服给药的具有临床意义的GABA相关化合物的递送途径的治疗潜力。
