Cogan M G
Am J Physiol. 1983 Aug;245(2):F272-5. doi: 10.1152/ajprenal.1983.245.2.F272.
The present study quantitated the effect of extracellular volume expansion on absolute proximal bicarbonate, chloride, and water reabsorption in 10 Sprague-Dawley rats. Paired free-flow micropuncture measurements were made in the plasma-replete euvolemic state and following 10% body wt isohydric, colloid-free volume expansion. Single nephron glomerular filtration rate and glomerular ultrafiltrate concentration of bicarbonate and chloride were similar in the two conditions. Volume expansion caused absolute proximal reabsorption of bicarbonate to fall by only 7% (from 987 +/- 39 to 920 +/- 53 pmol/min, P less than 0.05). This decrement in bicarbonate reabsorption was compatible with the known increase in bicarbonate permeability and backleak induced by expansion. In contrast, a marked 26% fall in absolute proximal chloride reabsorption occurred (from 1,601 +/- 147 to 1,180 +/- 149 peq/min, P less than 0.005), attributed to alteration in transcellular rather than passive sodium chloride transport. Thus, the decrease in absolute proximal volume reabsorption (from 19.7 +/- 1.0 to 16.7 +/- 1.2 nl/min, P less than 0.005) induced by volume expansion was predominantly a consequence of inhibition of sodium chloride rather than sodium bicarbonate reabsorption.
本研究对10只Sprague-Dawley大鼠细胞外液量扩张对近端小管碳酸氢盐、氯离子和水的绝对重吸收的影响进行了定量分析。在血浆充足的等容状态下以及10%体重的等渗、无胶体液量扩张后，进行了配对自由流微穿刺测量。在这两种情况下，单肾单位肾小球滤过率以及肾小球超滤液中碳酸氢盐和氯离子的浓度相似。液量扩张导致近端小管碳酸氢盐的绝对重吸收仅下降7%（从987±39降至920±53 pmol/min，P<0.05）。碳酸氢盐重吸收的这种下降与已知的扩张诱导的碳酸氢盐通透性增加和回漏相符合。相比之下，近端小管氯离子的绝对重吸收显著下降了26%（从1601±147降至1180±149 peq/min，P<0.005），这归因于跨细胞而非被动的氯化钠转运的改变。因此，液量扩张引起的近端小管绝对液量重吸收的下降（从19.7±1.0降至16.7±1.2 nl/min，P<0.005）主要是氯化钠而非碳酸氢钠重吸收受到抑制的结果。
