Chesney R W, Gusowski N, Dabbagh S, Theissen M, Padilla M, Diehl A
Biochim Biophys Acta. 1985 Feb 14;812(3):702-12. doi: 10.1016/0005-2736(85)90264-0.
The effect of a variety of ions and other solutes on the accumulation of the beta-amino acid, taurine, was examined in rat renal brush-border membrane vesicles. Initial taurine uptake (15 and 30 s) is sodium-dependent with a typical overshoot. This Na+ effect was confirmed by exchange diffusion and gramicidin inhibition of taurine uptake. External K+ or Li+ do not increase taurine accumulation more than Na+-free mannitol, except that the combination of external K+ and Na+ in the presence of nigericin enhances uptake. Of all anions tested, including more permeant (SCN- and NO3-) or less permeant (SO4(2-)), chloride supported taurine accumulation to a significantly greater degree. Preloading vesicles with choline chloride reduced taurine uptake, suggesting that external Cl- stimulates uptake. Since this choline effect could be related to volume change, due to the slow diffusion of choline into vesicles, brush-border membrane vesicles were pre-incubated with LiCl, LiNO3 and LiSO4. Internal LiCl, regardless of the final Na+ anion mixture, reduced initial rate (15 and 60 s) and peak (360 s) taurine uptake. Internal LiNO3 or LiSO4 with external NaCl resulted in similar or higher values of uptake at 15, 60 and 360 s, indicating a role for external Cl- in taurine uptake in addition to Na+ effect. Although uptake by vesicles is greatest at pH 8.0 and inhibited at acidic pH values (pH less than 7.0), an externally directed H+ gradient does not influence uptake. Similarly, amiloride, an inhibitor of the Na+/H+ antiporter, had no influence on taurine accumulation over a wide variety of concentrations or at low Na+ concentrations. Taurine uptake is blocked only by other beta-amino acids and in a competitive fashion. D-Glucose and p-aminohippurate at high concentrations (greater than 10(-3) M) reduce taurine uptake, possibly by competing for sodium ions, although gramicidin added in the presence of D-glucose inhibits taurine uptake even further. These studies more clearly define the nature of the renal beta-amino acid transport system in brush-border vesicles and indicate a role for external Cl- in this uptake system.
在大鼠肾刷状缘膜囊泡中研究了多种离子和其他溶质对β-氨基酸牛磺酸积累的影响。牛磺酸的初始摄取（15秒和30秒）依赖于钠，具有典型的超调现象。通过交换扩散和短杆菌肽对牛磺酸摄取的抑制作用证实了这种Na⁺效应。除了在尼日利亚菌素存在下外部K⁺和Na⁺的组合增强摄取外，外部K⁺或Li⁺对牛磺酸积累的增加并不超过无Na⁺甘露醇。在所有测试的阴离子中，包括通透性较高的（SCN⁻和NO₃⁻）或通透性较低的（SO₄²⁻），氯化物对牛磺酸积累的支持程度明显更高。用氯化胆碱预加载囊泡会降低牛磺酸摄取，表明外部Cl⁻刺激摄取。由于这种胆碱效应可能与体积变化有关，由于胆碱向囊泡内扩散缓慢，刷状缘膜囊泡用LiCl、LiNO₃和LiSO₄进行预孵育。内部LiCl，无论最终的Na⁺阴离子混合物如何，都会降低初始速率（15秒和60秒）和峰值（360秒）牛磺酸摄取。内部LiNO₃或LiSO₄与外部NaCl一起在15、60和360秒时导致相似或更高的摄取值，表明除了Na⁺效应外，外部Cl⁻在牛磺酸摄取中也起作用。尽管囊泡摄取在pH 8.0时最大，在酸性pH值（pH小于7.0）时受到抑制，但外向的H⁺梯度并不影响摄取。同样，Na⁺/H⁺反向转运体抑制剂氨氯地平在各种浓度或低Na⁺浓度下对牛磺酸积累均无影响。牛磺酸摄取仅被其他β-氨基酸以竞争性方式阻断。高浓度（大于10⁻³ M）的D-葡萄糖和对氨基马尿酸盐会降低牛磺酸摄取，可能是通过竞争钠离子，尽管在D-葡萄糖存在下添加短杆菌肽会进一步抑制牛磺酸摄取。这些研究更清楚地界定了肾刷状缘囊泡中β-氨基酸转运系统的性质，并表明外部Cl⁻在该摄取系统中的作用。
