Quamme G A
Can J Physiol Pharmacol. 1981 Feb;59(2):122-30. doi: 10.1139/y81-021.
Superficial nephrons were perfused in vivo to determine the effect of intraluminal sulfate (1--20 mM) on electrolyte reabsorption in the rat with special reference to calcium and magnesium transport. This technique allowed us the opportunity of investigating separate electrolyte transfers without alteration of extrarenal influences. The major amount of perfused sulfate was absorbed in the proximal tubule with little absorption distal to the late proximal collection site. Phosphate transport was affected by high luminal sulfate concentrations indicating distinct reabsorptive mechanisms for these two anions. Intraluminal sulfate significantly inhibited calcium and magnesium reabsorption in the proximal tubule, loop of Henle, and superficial distal tubule, in distinction to modest effects on sodium transport in these nephron segments. Chloride transport was not altered. The inhibition of divalent cation transfer was not quantitatively similar in the different tubule segments. Small amounts of sulfate completely inhibited proximal calcium and magnesium reabsorption with little effect on transport within the loop of Henle. Enhanced distal delivery of sulfate significantly inhibited calcium and magnesium reabsorption in the distal tubule, a site where the sulfate anion is not reabsorbed. These results demonstrate the importance of distal delivery of anionic ligands capable of forming nonreabsorbable complexes. Thus distal calcium and magnesium transport may be greatly modified by proximal control of anion reabsorption.
对浅表肾单位进行体内灌注，以确定管腔内硫酸盐（1-20 mM）对大鼠电解质重吸收的影响，特别关注钙和镁的转运。该技术使我们有机会在不改变肾外影响的情况下研究单独的电解质转运。灌注的硫酸盐大部分在近端小管被吸收，在近端集合位点后期远端几乎没有吸收。高管腔硫酸盐浓度影响磷酸盐转运，表明这两种阴离子有不同的重吸收机制。管腔内硫酸盐显著抑制近端小管、髓袢和浅表远端小管中的钙和镁重吸收，与这些肾单位节段中对钠转运的适度影响不同。氯的转运没有改变。不同肾小管节段中二价阳离子转运的抑制在数量上不相似。少量硫酸盐完全抑制近端钙和镁重吸收，对髓袢内的转运影响很小。硫酸盐向远端的输送增强显著抑制远端小管中的钙和镁重吸收，在该部位硫酸根阴离子不被重吸收。这些结果证明了能够形成不可重吸收复合物的阴离子配体向远端输送的重要性。因此，近端对阴离子重吸收的控制可能会极大地改变远端钙和镁的转运。
