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目的 探讨大鼠低亲和力钠依赖二羧酸转运蛋白(SDCT1)对枸橼酸及草酸的转 运特点。方法 克隆出大鼠SDCT1全长cDNA基因。应用爪蟾卵母细胞异源性表达SDCT1,并 使用双电极电压钳法记录通道电流。通过改变灌流液中枸橼酸、草酸的浓度,以及两种底物转运 时钠离子的浓度及pH值,对其特性进行了研究。结果SDCT1对枸橼酸及草酸的转运均为底 物浓度及钠离子依赖。pH值变化显著影响2者的转运。但低pH对草酸的转运影响要远大于枸 橼酸。结论 在临床实践中,虽然升高尿液pH值可以抑制枸橼酸的重吸收,发挥其抑制钙盐沉 积的功能。但过度地碱化尿液也会使草酸的重吸收受到抑制,使草酸大量存留在尿中而导致结 石。保持适当的尿酸碱度是必要的。
Objective To investigate the transport characteristics of citrate and oxalic acid by low-affinity sodium-dependent dicarboxylate transporter (SDCT1) in rats. Methods The full-length cDNA of rat SDCT1 was cloned. Xenopus oocytes were used to express SDCT1 heterologously and channel currents were recorded using a bipolar voltage clamp method. By changing the concentrations of citrate and oxalic acid in the perfusate and the sodium ion concentration and pH of the two substrates during transport, the characteristics were studied. Results The transport of SDCT1 to citrate and oxalate was both substrate concentration and sodium ion dependence. Changes in pH significantly affect the transport of both. However, the effect of low pH on oxalate transport is much greater than that of citric acid. Conclusion In clinical practice, although increasing urine pH can restrain citric acid reabsorption and exert its function of inhibiting calcium deposition. However, over-alkalization of urine will also inhibit the reabsorption of oxalic acid, leaving a large number of oxalic acid in the urine and lead to stones. Maintaining appropriate urinary pH is necessary.