Rajerison R M, Faure M, Morel F
Pflugers Arch. 1986 Mar;406(3):291-5. doi: 10.1007/BF00640916.
The effects of 20 mumol/l amiloride, 10 mumol/l furosemide and 1 mmol/l ouabain on cell Na and K concentrations were investigated by flame microphotometry in isolated rat medullary collecting tubules and medullary thick ascending limbs (MCT and MAL) as a function of the external potassium concentration [Ke]. The results are expressed as Na and K concentrations per liter cell volume ([Nac] and [Kc], mmol/l) and relative sodium content, [Nac]/([Nac] + [Kc]). From the experimental curves, [Ke]1/2 is defined as the [Ke] value corresponding to half maximal exchange of K against Na in cells. When [Ke] was 5 mmol/l, the relative Na content was less than 15% in control and amiloride-treated MCT as well as in control and furosemide-treated MAL, and about 24% in ouabain-treated MCT and MAL. In MCT, relative cell Na content increased up to 90% or more when [Ke] was reduced from 2.5 to 0.25 mmol/l. [Ke]1/2 was 0.55, 0.45 and 1.25 mmol/l for control, amiloride-treated and ouabain-treated MCT respectively. In MAL, similar increases in relative Na content were observed when [Ke] was reduced from 0.5 to 0.05 mmol/l. [Ke]1/2 was 0.25, 0.10 and 1.75 mmol/l for control, furosemide-treated and ouabain-treated MAL respectively. When [Ke] was reduced from 5 to 1 mmol/l, [Nac] dropped from 16.4 to 8.4 mmol/l (P less than 0.01) in control MAL. When [Ke] was 5 mmol/l, [Nac] was lower in furosemide-treated MAL (7.8 mmol/l) than control MAL (P less than 0.01). At 1 mmol/l [Ke], [Nac] was similar in both groups. These results are discussed in terms of the balance between the active and passive components of Na and K fluxes across apical and basolateral cell membranes. They indicate that a K-dependent passive Na entry process exists in the membranes of MAL cells but not of MCT cells. This process was proportionally more inhibited than the active Na pump when [Ke] was reduced from 5 to 1 mmol/l. In addition, it was found sensitive to furosemide.(ABSTRACT TRUNCATED AT 250 WORDS)
采用火焰光度法，在离体大鼠髓质集合管和髓袢升支粗段（MCT和MAL）中，研究了20 μmol/l氨氯吡咪、10 μmol/l呋塞米和1 mmol/l哇巴因对细胞钠和钾浓度的影响，这些影响是细胞外钾浓度[Ke]的函数。结果以每升细胞体积的钠和钾浓度（[Nac]和[Kc]，mmol/l）以及相对钠含量[Nac]/（[Nac] + [Kc]）表示。根据实验曲线，[Ke]1/2定义为细胞中钾与钠进行半最大交换时对应的[Ke]值。当[Ke]为5 mmol/l时，对照和氨氯吡咪处理的MCT以及对照和呋塞米处理的MAL中的相对钠含量低于15%，而哇巴因处理的MCT和MAL中的相对钠含量约为24%。在MCT中，当[Ke]从2.5 mmol/l降至0.25 mmol/l时，相对细胞钠含量增加至90%或更高。对照、氨氯吡咪处理和哇巴因处理的MCT的[Ke]1/2分别为0.55、0.45和1.25 mmol/l。在MAL中，当[Ke]从0.5 mmol/l降至0.05 mmol/l时，观察到相对钠含量有类似增加。对照、呋塞米处理和哇巴因处理的MAL的[Ke]1/2分别为0.25、0.10和1.75 mmol/l。当[Ke]从5 mmol/l降至1 mmol/l时，对照MAL中的[Nac]从16.4 mmol/l降至8.4 mmol/l（P<0.01）。当[Ke]为5 mmol/l时，呋塞米处理的MAL中的[Nac]（7.8 mmol/l）低于对照MAL（P<0.01）。在[Ke]为1 mmol/l时，两组中的[Nac]相似。根据跨顶端和基底外侧细胞膜的钠和钾通量的主动和被动成分之间的平衡对这些结果进行了讨论。结果表明，MAL细胞的膜中存在钾依赖性被动钠进入过程，而MCT细胞的膜中不存在。当[Ke]从5 mmol/l降至1 mmol/l时，该过程比主动钠泵受到的抑制作用更大。此外，发现该过程对呋塞米敏感。（摘要截短于250字）
