Kennedy D J, Raldua D, Thwaites D T
Institute for Cell & Molecular Biosciences, Faculty of Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, NE2 4HH, UK.
Cell Mol Life Sci. 2005 Jul;62(14):1621-31. doi: 10.1007/s00018-005-5078-3.
Selective pharmacological Na+/H+ exchange (NHE) inhibitors were used to identify functional NHE isoforms in human small intestinal enterocytes (Caco-2) and to distinguish between direct and indirect effects on transport via the intestinal di/tripeptide transporter hPepT1. The relative potencies of these inhibitors to inhibit 22Na+ influx identifies NHE3 and NHE1 as the apical and basolateral NHE isoforms. The Na+-dependent (NHE3-sensitive) component of apical dipeptide ([14C] Gly-Sar) uptake was inhibited by the selective NHE inhibitors with the same order of potency observed for inhibition of apical 22Na+ uptake. However, 5-(N-ethyl-N-isopropyl) amiloride (EIPA) also reduced [14C]Gly-Sar uptake in the absence of Na+ and this inhibition was concentration and pH (maximal at pH 5.5) dependent. NHE3 inhibition by S1611 and S3226 modulates dipeptide uptake indirectly by reducing the transapical driving force (H+ electrochemical gradient). EIPA (at 100 microM) has similar effects, but at higher concentrations (> 200 microM) also has direct inhibitory effects on hPepT1.
使用选择性药理学Na+/H+交换（NHE）抑制剂来鉴定人小肠肠上皮细胞（Caco-2）中的功能性NHE亚型，并区分对通过肠二肽/三肽转运体hPepT1转运的直接和间接影响。这些抑制剂抑制22Na+内流的相对效力确定NHE3和NHE1分别为顶端和基底外侧的NHE亚型。顶端二肽（[14C]甘氨酰-肌氨酸）摄取的Na+依赖性（对NHE3敏感）成分被选择性NHE抑制剂抑制，其效力顺序与抑制顶端22Na+摄取时观察到的相同。然而，5-（N-乙基-N-异丙基）阿米洛利（EIPA）在无Na+时也降低了[14C]甘氨酰-肌氨酸的摄取，且这种抑制作用依赖于浓度和pH（在pH 5.5时最大）。S1611和S3226对NHE3的抑制通过降低跨顶端驱动力（H+电化学梯度）间接调节二肽摄取。EIPA（100 microM）有类似作用，但在较高浓度（>200 microM）时也对hPepT1有直接抑制作用。
