Elsevier

Kidney International

Volume 84, Issue 2, August 2013, Pages 277-284
Kidney International

Basic Research
The calcium sensing receptor modulates fluid reabsorption and acid secretion in the proximal tubule

https://doi.org/10.1038/ki.2013.137Get rights and content
Under an Elsevier user license
open archive

The proximal tubule uses a complex process of apical acid secretion and basolateral bicarbonate absorption to regulate both luminal acidification and fluid absorption. One of the primary regulators of apical acid secretion is the luminal sodium–hydrogen exchanger expressed along the apical membrane of the proximal tubule. Similarly, the calcium-sensing receptor (CaSR) is also located along the luminal membrane of the proximal tubule. Here we investigated the role of CaSR in proton secretion and fluid reabsorption in proximal tubules by modulating luminal calcium concentration, using both in vivo micropuncture in rats and in vitro perfused mouse proximal tubules. Using CaSR knockout mice and a calcimimetic agent, we found that increased proton secretion and fluid reabsorption were CaSR dependent. Activating CaSR by either raising the luminal calcium ion concentration or by the calcimimetic caused a concomitant increase in sodium-dependent proton extrusion and fluid reabsorption, whereas in proximal tubules isolated from CaSR knockout mice varying calcium ion concentration had no effect. Application of a calcimimetic in lower concentrations of calcium ion stimulated these processes in vitro and in vivo. Thus, in both rats and mice, increased luminal calcium concentration leads to enhanced fluid reabsorption in the proximal tubule, a process related to activation of CaSR.

KEYWORDS

calcium-sensing receptor
intracellular pH
ion transport
kidney stones
kidney tubule

Cited by (0)