Eveloff J, Kinne R
J Membr Biol. 1983;72(3):173-81. doi: 10.1007/BF01870584.
Sodium transport mechanisms were investigated in plasma membrane vesicles prepared from the medullary thick ascending limb of Henle's loop (TALH) of rabbit kidney. The uptake of 22Na into the plasma membrane vesicles was investigated by a rapid filtration technique. Sodium uptake was greatest in the presence of chloride; it was reduced when chloride was replaced by nitrate, gluconate or sulfate. The stimulation of sodium uptake by chloride was seen in the presence of a chloride gradient directed into the vesicle and when the vesicles were equilibrated with NaCl, KCl plus valinomycin so that no chemical or electrical gradients existed across the vesicle (tracer exchange experiments). Furosemide decreased sodium uptake into the vesicles in a dose-dependent manner only in the presence of chloride, with a Ki of around 5 X 10(-6) M. Amiloride, at 2 mM, had no effect on the chloride-dependent sodium uptake. Similarly, potassium removal had no effect on the chloride-dependent sodium uptake and furosemide was an effective inhibitor of sodium uptake in a potassium-free medium. The results show the presence of a furosemide-sensitive sodium-chloride cotransport system in the plasma membranes of the medullary TALH. There is no evidence for a Na+/H+ exchange mechanism or a Na+ -K+ -Cl- cotransport system. The sodium-chloride cotransport system would effect the uphill transport of chloride against its electrochemical potential gradient at the luminal membrane of the cell.
对取自兔肾髓袢升支粗段（TALH）制备的质膜囊泡中的钠转运机制进行了研究。采用快速过滤技术研究了质膜囊泡对22Na的摄取。在有氯离子存在时，钠摄取量最大；当氯离子被硝酸盐、葡萄糖酸盐或硫酸盐取代时，摄取量降低。在存在指向囊泡内的氯离子梯度时，以及当囊泡用NaCl、KCl加缬氨霉素平衡，使得囊泡两侧不存在化学或电势梯度时（示踪剂交换实验），可见氯离子对钠摄取的刺激作用。呋塞米仅在有氯离子存在时以剂量依赖方式降低囊泡对钠的摄取，其抑制常数（Ki）约为5×10(-6)M。2 mM的氨氯吡脒对氯离子依赖的钠摄取无影响。同样，去除钾对氯离子依赖的钠摄取无影响，并且呋塞米在无钾培养基中是钠摄取的有效抑制剂。结果表明，髓袢升支粗段质膜中存在对呋塞米敏感的钠-氯共转运系统。没有证据表明存在Na+/H+交换机制或Na+-K+-Cl-共转运系统。钠-氯共转运系统将在细胞管腔膜处逆着其电化学势梯度进行氯离子的上坡转运。
