Metabolic acidosis stimulates bicarbonate reabsorption in the early proximal tubule.
Metabolic acidosis stimulates bicarbonate reabsorption in the early proximal tubule.
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DOI：
10.1152/ajprenal.1989.257.1.f35
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发表时间：
1989-07
期刊：
影响因子：
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通讯作者：
R. Santella;F. Gennari;D. A. Maddox
中科院分区：
文献类型：
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作者：
R. Santella;F. Gennari;D. A. Maddox
早期近端小管是肾脏重吸收碳酸氢盐的主要部位，但酸中毒对这一段转运的影响知之甚少。本研究检查了慢性代谢性酸中毒（MA）大鼠（由NH 4Cl给药诱导）的早期近端碳酸氢盐重吸收。通过自由流动显微穿刺技术对大鼠进行了研究，在不同程度的血浆体积膨胀后改变碳酸氢盐（FLHCO 3）的过滤负荷。在FLHCO 3小于700 pmol/min时，对照组和酸中毒动物在距离Bowman间隙2 mm处重吸收了超过80%的过滤负荷。在较高的FLHCO 3（700- 1，100 pmol/min）下，MA大鼠早期近端小管的重吸收显著高于对照组（633 +/- 26 vs. 449 +/- 24 pmol/min，距离Bowman间隙1 - 2 mm，P <0.001）。这种MA诱导的早期近端碳酸氢盐重吸收的刺激通过急性低碳酸血症或碱输注将全身pH恢复至正常而完全逆转。因此，当血浆扩张增加碳酸氢盐输送时，MA大鼠早期近端小管的碳酸氢盐重吸收与全身pH值变化密切相关。这种效应的机制仍有待确定。
The early proximal tubule is the major site for renal bicarbonate reabsorption but little is known about the influence of acidosis on transport in this segment. This study examined early proximal bicarbonate reabsorption in rats with chronic metabolic acidosis (MA) (induced by NH4Cl administration). Rats were studied by free-flow micropuncture techniques, after varying degrees of plasma volume expansion to vary the filtered load of bicarbonate (FLHCO3). At FLHCO3 less than 700 pmol/min, both control and acidotic animals reabsorbed greater than 80% of the filtered load by 2 mm from Bowman's space. At higher FLHCO3 (700-1,100 pmol/min), reabsorption in the early proximal tubule was significantly greater in MA rats vs. control (633 +/- 26 vs. 449 +/- 24 pmol/min, between 1 and 2 mm from Bowman's space, P less than 0.001). This MA-induced stimulation of early proximal bicarbonate reabsorption was completely reversed by restoring systemic pH to normal either by acute hypocapnia or alkali infusion. Thus bicarbonate reabsorption in the early proximal tubule correlated closely with changes in systemic pH in rats with MA when bicarbonate delivery was increased by plasma expansion. The mechanism of this effect remains to be determined.