Leyssac P P, Holstein-Rathlou N H, Skøtt P, Alfrey A C
University Institute of Experimental Medicine, Panum Institute, Copenhagen, Denmark.
Am J Physiol. 1990 Apr;258(4 Pt 2):F1090-5. doi: 10.1152/ajprenal.1990.258.4.F1090.
Lithium and sodium are normally reabsorbed in parallel with water by the renal proximal tubule whereby their tubular fluid-to-plasma concentration ratios (TF/P) remain close to unity throughout the proximal convoluted segment. During osmotic diuresis, the late proximal (TF/P)Na is known to decrease. The present experiments were undertaken to study whether the late proximal TF/P for Li decreases like that of Na during osmotic diuresis. Data were obtained in a control period (C) and in two successive periods during mannitol diuresis (P1, P2). Glomerular filtration rate decreased gradually during osmotic diuresis [1,147 +/- 32 (C) to 950 +/- 22 (P2) microliters.min-1.g kidney wt (KW)-1, P less than 0.01), whereas Li clearance (CLi) increased [377 +/- 21 (C) to 469 +/- 28 (P1, P less than 0.01) and 408 +/- 25 (P2, NS) microliters.min-1.gKW-1, respectively]. (TF/P)Na decreased from 0.98 +/- 0.02 (C) to 0.89 +/- 0.02 (P less than 0.01) and 0.90 +/- 0.04 (P less than 0.05) (P1 and P2, respectively). (TF/P)Li was close to, but significantly higher than, unity during control (1.09 +/- 0.02), but, in contrast to (TF/P)Na, it did not decrease significantly during osmotic diuresis. Delivery of water from the proximal straight segment, as estimated from CLi/CIn, increased in proportion to the delivery from the convoluted segment, as estimated from 1/(TF/P)In. It is concluded that the proximal net Li reabsorption follows more closely the net water reabsorption than the net Na reabsorption during osmotic diuresis.
锂和钠通常在肾近端小管与水同时被重吸收，因此在整个近曲小管段它们的肾小管液与血浆浓度比（TF/P）保持接近1。在渗透性利尿期间，已知近端晚期的（TF/P）Na会降低。进行本实验是为了研究在渗透性利尿期间，锂的近端晚期TF/P是否会像钠那样降低。数据是在一个对照期（C）以及甘露醇利尿的两个连续时期（P1、P2）获得的。在渗透性利尿期间肾小球滤过率逐渐降低[1,147±32（C）至950±22（P2）微升·分钟-1·克肾重（KW）-1，P<0.01]，而锂清除率（CLi）增加[分别为377±21（C）至469±28（P1，P<0.01）和408±25（P2，无显著差异）微升·分钟-1·克KW-1]。（TF/P）Na从0.98±0.02（C）降至0.89±0.02（P<0.01）和0.90±0.04（P<0.05）（分别为P1和P2）。（TF/P）Li在对照期间接近但显著高于1（1.09±0.02），但与（TF/P）Na不同，在渗透性利尿期间它没有显著降低。从CLi/CIn估算的近端直段水的输送量，与从1/（TF/P）In估算的曲段水的输送量成比例增加。得出的结论是，在渗透性利尿期间，近端锂的净重吸收比净钠重吸收更紧密地跟随净水重吸收。
