Lostao M P, Mata J F, Larrayoz I M, Inzillo S M, Casado F J, Pastor-Anglada M
Departamento de Fisiologia y Nutrición, Universidad de Navarra, Pamplona, Spain.
FEBS Lett. 2000 Sep 15;481(2):137-40. doi: 10.1016/s0014-5793(00)01983-9.
The concentrative pyrimidine-preferring nucleoside transporter 1 (hCNT1), cloned from human fetal liver, was expressed in Xenopus laevis oocytes. Using the two-electrode voltage-clamp technique, it is shown that translocation of nucleosides by this transporter generates sodium inward currents. Membrane hyperpolarization (from -50 to -150 mV) did not affect the K(0.5) for uridine, although it increased the transport current approximately 3-fold. Gemcitabine (a pyrimidine nucleoside-derived drug) but not fludarabine (a purine nucleoside-derived drug) induced currents in oocytes expressing the hCNT1 transporter. The K(0.5) value for gemcitabine at -50 mV membrane potential was lower than that for natural substrates, although this drug induced a lower current than uridine and cytidine, thus suggesting that the affinity binding of the drug transporter is high but that translocation occurs more slowly. The analysis of the currents generated by the hCNT1-mediated transport of nucleoside-derived drugs used in anticancer and antiviral therapies will be useful in the characterization of the pharmacological profile of this family of drug transporters and will allow rapid screening for uptake of newly developed nucleoside-derived drugs.
从人胎肝中克隆出的浓缩型嘧啶偏好性核苷转运体1（hCNT1）在非洲爪蟾卵母细胞中表达。采用双电极电压钳技术表明，该转运体介导的核苷转运产生内向钠电流。膜超极化（从-50 mV至-150 mV）虽使尿苷的半数转运浓度（K(0.5)）不变，但使转运电流增加约3倍。吉西他滨（一种嘧啶核苷衍生药物）而非氟达拉滨（一种嘌呤核苷衍生药物）可在表达hCNT1转运体的卵母细胞中诱导电流。在膜电位为-50 mV时，吉西他滨的K(0.5)值低于天然底物，尽管该药物诱导的电流低于尿苷和胞苷，这表明药物与转运体的亲和力高，但转运发生得更慢。分析hCNT1介导的用于抗癌和抗病毒治疗的核苷衍生药物转运所产生的电流，将有助于表征该类药物转运体的药理学特征，并可快速筛选新开发的核苷衍生药物的摄取情况。
