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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Evidence from renal proximal tubules that HCO_3 and solute reabsorption are acutely regulated not by pH but by basolateral HCO_3~- and CO_2
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Evidence from renal proximal tubules that HCO_3 and solute reabsorption are acutely regulated not by pH but by basolateral HCO_3~- and CO_2

机译：肾近端小管的证据表明，HCO_3和溶质的重吸收不受pH的影响，而受基底外侧HCO_3〜-和CO_2的影响

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摘要

Respiratory acidosis, a decrease in blood pH caused by a rise in [CO_2], rapidly triggers a compensatory response in which the kidney markedly increases its secretion of H~+ from blood to urine. However, in this and other acid-base disturbances, the equilibrium CO_2 + H_2O ←→ HCO_3~- + H~+ makes it impossible to determine whether the critical parameter is [CO_2], [HCO_3~-], and/or pH. Here, we used out-of-equilibrium CO_2/HCO_3~- solutions to alter basolateral (BL) [HCO_3~-], [CO_2], or pH, systematically and one at a time, on isolated perfused S2 rabbit proximal tubules. We found that increasing [HCO_3~-]_(BL) from 0 to 44 mM, at a fixed [CO_2]_(BL) of 5% and a fixed pH_(BL) of 7.40, caused HCO_3~- reabsorption (J_(Hco_3)) to fall by half but did not significantly affect volume reabsorption (J_v)· Increasing [CO_2]_(BL) from 0% to 20%, at a fixed [HCO_3~-]_(BL) of 22 mM and pH_(BL) of 7.40, caused J_(HCO_3) to rise 2.5-fold but did not significantly affect J_v· Finally, increasing pH_(BL) from 6.80 to 8.00, at a fixed [HCO_3~-]_(BL) of 22 mM and [CO_2]_(BL) of 5%, did not affect either J_(Hco_3) or J_v· Analysis of the J_(Hco_3) and J_v data implies that, as the tubule alters J_(Hco_3), it compensates the reabsorption of other solutes to keep J_v approximately constant. Because the cells cannot respond acutely to pH changes, we propose that the responses of J_(Hco_3) and the reabsorption of other solutes to changes in [HCO_3~-]_(BL)or [CO_2]_(BL) involve sensors for basolateral HCO_3~- and CO_2.
机译：呼吸性酸中毒是由[CO_2]升高引起的血液pH值下降，迅速触发代偿反应，其中肾脏显着增加了H〜+从血液到尿液的分泌。但是，在这种和其他酸碱干扰下，平衡的CO_2 + H_2O←→HCO_3〜-+ H〜+使得无法确定关键参数是[CO_2]，[HCO_3〜-]和/或pH值。在这里，我们使用不平衡的CO_2 / HCO_3〜-溶液系统地，一次一次地在分离的灌注S2兔近端小管上一次改变基底外侧（BL）[HCO_3〜-]，[CO_2]或pH。我们发现，将[HCO_3〜-] _（BL）从0增加到44 mM，在固定的[CO_2] _（BL）为5％和固定的pH_（BL）为7.40的情况下，会导致HCO_3〜-重吸收（J_（ Hco_3））下降一半，但并未显着影响体积重吸收（J_v）·在固定[HCO_3〜-] _（BL）为22 mM和pH_的情况下，[CO_2] _（BL）从0％增加到20％ （BL）为7.40，导致J_（HCO_3）升高2.5倍，但对J_v的影响不明显。最后，以22 mM的固定[HCO_3〜-] _（BL）将pH_（BL）从6.80增加至8.00。和[CO_2] _（BL）为5％时，对J_（Hco_3）或J_v均无影响。对J_（Hco_3）和J_v数据的分析表明，随着肾小管改变J_（Hco_3），它补偿了小管的重吸收。其他溶质保持J_v近似恒定。由于细胞不能对pH值变化做出强烈反应，因此我们建议J_（Hco_3）和其他溶质对[HCO_3〜-] _（BL）或[CO_2] _（BL）变化的重吸收涉及基底外侧传感器HCO_3〜-和CO_2。

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