Departments of Medicine and Physiology, Case-Western Reserve University, Louis Stokes VAMC and Rammelkamp Center for Research, Metrohealth Medical Center, Cleveland, Ohio, USA.
Curr Opin Nephrol Hypertens. 2010 Jan;19(1):106-12. doi: 10.1097/MNH.0b013e328332e7b2.
A rise in extracellular Ca acting through the calcium sensing receptor (CaR) causes physiologically significant loss of Na, K, Cl, Ca, and water. The CaR is expressed in all nephron segments, but its effects on ion and water transport in specific segments as well as the mechanisms by which it regulates ion and water transport is not fully understood. This review will summarize recent information regarding the renal transport effects of the CaR.
Considerable progress has been made in characterizing TRPV5, the regulated Ca entry pathway in the distal convoluted tubule (DCT), but precisely how the CaR contributes to its regulation is not known. The CaR interacts with, and inactivates, a K channel, Kir4.1, in the renal distal convoluted tubule. Recently described loss-of-function mutations in this K channel lead to a complicated phenotype that includes salt wasting, suggesting that inactivation of Kir4.1 by the CaR may contribute to the salt wasting observed in response to CaR activation.
The CaR mediates the effects of extracellular Ca on the kidney and is an essential control point in regulation of Ca balance and possibly physiologic regulation of NaCl balance, but the circumstances for regulation of Na balance are not fully established in mammals. The thick ascending limb of Henle and the distal convoluted tubule appear to be the nephron segments most responsible for the effects of the CaR on ion and water transport, although its mechanisms of action are not fully established.
细胞外钙通过钙敏感受体（CaR）的作用导致钠、钾、氯、钙和水的生理显著丢失。CaR 在所有肾单位节段中均有表达，但它对特定节段的离子和水转运的影响以及它调节离子和水转运的机制尚未完全清楚。这篇综述将总结最近关于 CaR 对肾脏转运影响的信息。
在描述 TRPV5（远曲小管的调节钙内流途径）方面取得了相当大的进展，但 CaR 如何参与其调节尚不清楚。CaR 与肾远曲小管中的 K 通道 Kir4.1 相互作用并使其失活。最近描述的该 K 通道的功能丧失性突变导致一种复杂的表型，包括盐耗竭，这表明 CaR 对 Kir4.1 的失活可能导致 CaR 激活时观察到的盐耗竭。
CaR 介导细胞外钙对肾脏的作用，是钙平衡调节和可能的生理 NaCl 平衡调节的一个重要控制点，但哺乳动物中钠平衡的调节情况尚未完全确定。Henle 粗升支和远曲小管似乎是 CaR 对离子和水转运影响的主要负责的肾单位节段，尽管其作用机制尚未完全确定。
