Corman B, Roinel N, de Rouffignac C
J Membr Biol. 1981;62(1-2):105-11. doi: 10.1007/BF01870204.
The relationship between water and sodium movements through the mammalian proximal convoluted tubule was investigated by substituting lithium for sodium. Proximal convoluted rat Kidney tubules were perfused in vivo with a Ringer solution containing 107 meq/liter lithium and 42 meq/liter sodium. Several micropunctures were made along the same nephron, and [3H] inulin, [14C] glucose, 22Na, osmolality, Na, Mg and Cl were determined on each sample. Measurements of 22Na showed that sodium and lithium diffusion rates were practically identical throughout the entire epithelium. A one- for-one exchange of sodium for lithium induced a negative transepithelial net flux of Na from plasma to lumen. However, despite this negative flux, a positive net water movement was measured from lumen to plasma. This movement was proportional both to glucose reabsorption and to the rise in the chloride concentration, two mechanisms known to be dependent on the transcellular movement of sodium. It was therefore concluded that the net water flux was a function of the unidirectional transcellular net flux of Na. Rabbit proximal convoluted tubules were perfused in vitro with solution containing 75 meq/liter Li and 75 meq/liter Na on both the luminal and peritubular sides. Under these conditions, the water reabsorption rate dropped to half its control value. Water movement was therefore a function of the external sodium concentration, which in turn probably regulates the intracellular Na concentration.
通过用锂替代钠，研究了水和钠在哺乳动物近端曲管中的移动关系。给大鼠的近端曲管在体灌注含107毫当量/升锂和42毫当量/升钠的林格溶液。沿着同一条肾单位进行多次微穿刺，并测定每个样本中的[3H]菊粉、[14C]葡萄糖、22Na、渗透压、Na、Mg和Cl。22Na的测量结果表明，在整个上皮细胞中，钠和锂的扩散速率实际上是相同的。钠与锂一对一的交换导致Na从血浆到管腔的跨上皮净通量为负。然而，尽管存在这种负通量，但仍测量到从管腔到血浆的正净水流。这种水流与葡萄糖重吸收以及氯离子浓度的升高成正比，这两种机制已知依赖于钠的跨细胞移动。因此得出结论，净水通量是Na单向跨细胞净通量的函数。在体外给兔近端曲管的管腔侧和管周侧灌注含75毫当量/升Li和75毫当量/升Na的溶液。在这些条件下，水重吸收率降至其对照值的一半。因此，水的移动是外部钠浓度的函数，而外部钠浓度反过来可能调节细胞内Na浓度。
