Rajerison R M, Faure M, Morel F
Pflugers Arch. 1986 Mar;406(3):285-90. doi: 10.1007/BF00640915.
Cell Na+ and K+ contents were measured by flame photometry in single pieces of rat medullary thick ascending limb (MAL) and medullary collecting tubules (MCT) after an overnight incubation at various temperatures. Below 8 degrees C, MCT samples were no more able to sustain high-K+, low-Na+ cell concentrations, and sodium progressively replaced cell potassium as the temperature decreased. The loss of potassium and the accompanying accumulation of sodium by MCT cells occurred at lower or higher temperature when amiloride (20 mumol/l) or ouabain (1 mmol/l) was present respectively in the incubation medium compared to that observed on control non-treated MCT. In contrast, MAL samples maintained normal cation gradients across their membrane at all temperatures, including 0 degree C, even in the presence of ouabain. However, MAL cells lost nearly all their potassium which was replaced by sodium when they were incubated in K+-free solution. These Na+-loaded, K+-depleted MAL cells restored high-K+ and low-Na+ contents similar to those of control samples when they were further incubated for 1 h at 0 degree C in presence of 5 mmol/l external potassium. Even in the presence of 1 mmol/l ouabain and at 0 degree C, a restoration of almost normal cation gradients occurred provided that Na+-loaded MAL were incubated for 24 h after potassium addition to the external medium. The results are discussed in relation to the respective effects of low temperatures on the passive and active components of the cation balance in the cells of the two nephron segments.
在不同温度下过夜孵育后，通过火焰光度法测量大鼠髓质厚升支（MAL）和髓质集合管（MCT）单个样本中的细胞钠和钾含量。在8摄氏度以下，MCT样本无法再维持高钾、低钠的细胞浓度，随着温度降低，钠逐渐取代细胞内的钾。与未处理的对照MCT相比，当孵育培养基中分别存在氨氯吡咪（20 μmol/l）或哇巴因（1 mmol/l）时，MCT细胞钾的流失和伴随的钠积累在较低或较高温度下发生。相比之下，MAL样本在所有温度下，包括0摄氏度，即使存在哇巴因，也能维持跨膜的正常阳离子梯度。然而，当MAL细胞在无钾溶液中孵育时，它们几乎失去了所有的钾，被钠取代。当这些钠负载、钾耗尽的MAL细胞在5 mmol/l外部钾存在的情况下于0摄氏度进一步孵育1小时后，它们恢复了与对照样本相似的高钾和低钠含量。即使在存在1 mmol/l哇巴因且温度为0摄氏度的情况下，只要在外部培养基中添加钾后将钠负载的MAL孵育24小时，几乎正常的阳离子梯度就会恢复。讨论了低温对两个肾单位节段细胞阳离子平衡的被动和主动成分的各自影响的结果。
