optical-clearing-and-imaging-of-immunolabeled-kidney-tissue

Optical Clearing and Imaging of Immunolabeled Kidney Tissue

Optical clearing techniques render tissue transparent by equilibrating the refractive index throughout a sample for subsequent three-dimensional (3-D) ...

Oregon Health and Science University

The mammalian distal convoluted tubule (DCT) makes an important contribution to potassium homeostasis by modulating NaCl transport. The thiazide-sensitive Na/Cl cotransporter (NCC) is activated by low potassium intake and by hypokalemia. Coupled with suppression of aldosterone secretion, activation of NCC helps to retain potassium by increasing electroneutral NaCl reabsorption, therefore reducing Na/K exchange. Yet the mechanisms by which DCT cells sense plasma potassium concentration and transmit the information to the apical membrane are not clear. Here, we tested the hypothesis that the potassium channel Kir4.1 is the potassium sensor of DCT cells. We generated mice in which Kir4.1 could be deleted in the kidney after the mice are fully developed. Deletion of Kir4.1 in these mice led to moderate salt wasting, low BP, and profound potassium wasting. Basolateral membranes of DCT cells were depolarized, nearly devoid of conductive potassium transport, and unresponsive to plasma potassium concentration. Although renal WNK4 abundance increased after Kir4.1 deletion, NCC abundance and function decreased, suggesting that membrane depolarization uncouples WNK kinases from NCC. Together, these results indicate that Kir4.1 mediates potassium sensing by DCT cells and couples this signal to apical transport processes.

Potassium Sensing by Renal Distal Tubules Requires Kir4.1.

The aim of this mini review is to provide an overview regarding the role of inwardly rectifying potassium channel 4.1 (Kir4.1)/Kir5.1 in regulating renal K excretion. Deletion of Kir4.1 in the kidney inhibited thiazide-sensitive NaCl cotransporter (NCC) activity in the distal convoluted tubule (DCT) and slightly suppressed Na-K-2Cl cotransporter (NKCC2) function in the thick ascending limb (TAL). Moreover, increased dietary K intake inhibited, whereas decreased dietary K intake stimulated, the basolateral potassium channel (a Kir4.1/Kir5.1 heterotetramer) in the DCT. The alteration of basolateral potassium conductance is essential for the effect of dietary K intake on NCC because deletion of Kir4.1 in the DCT abolished the effect of dietary K intake on NCC. Since potassium intake-mediated regulation of NCC plays a key role in regulating renal K excretion and potassium homeostasis, the deletion of Kir4.1 caused severe hypokalemia and metabolic alkalosis under control conditions and even during increased dietary K intake. Finally, recent studies have suggested that the angiotensin II type 2 receptor (AT2R) and bradykinin-B2 receptor (BK2R) are involved in mediating the effect of high dietary K intake on Kir4.1/Kir5.1 in the DCT.

Article	Year
Potassium Sensing by Renal Distal Tubules Requires Kir4.1. Journal of the American Society of Nephrology : JASN\| PubMed ID: 28052988	2017
Kir4.1/Kir5.1 in the DCT plays a role in the regulation of renal K excretion. American journal of physiology. Renal physiology\| PubMed ID: 30623727	2019

Xiao-Tong Su

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