Faculté des sciences

Renal expression of parvalbumin is critical for NaCl handling and response to diuretics

Belge, Hendrica ; Gailly, Philippe ; Schwaller, Beat ; Loffing, Johannes ; Debaix, Huguette ; Riveira-Munoz, Eva ; Beauwens, Renaud ; Devogelaer, Jean-Pierre ; Hoenderop, Joost G. ; Bindels, René J. ; Devuyst, Olivier

In: Proceedings of the National Academy of Sciences of the United States of America, 2007, vol. 104, no. 37, p. 14849-14854

The distal convoluted tubule (DCT) plays an essential role in the reabsorption of NaCl by the kidney, a process that can be inhibited by thiazide diuretics. Parvalbumin (PV), a Ca²⁺-binding protein that plays a role in muscle fibers and neurons, is selectively expressed in the DCT, where its role remains unknown. We therefore investigated the renal phenotype of PV knockout mice... More

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    Summary
    The distal convoluted tubule (DCT) plays an essential role in the reabsorption of NaCl by the kidney, a process that can be inhibited by thiazide diuretics. Parvalbumin (PV), a Ca²⁺-binding protein that plays a role in muscle fibers and neurons, is selectively expressed in the DCT, where its role remains unknown. We therefore investigated the renal phenotype of PV knockout mice (Pvalb–/–) vs. wild-type (Pvalb+/+) littermates. PV colocalized with the thiazide-sensitive Na⁺-Cl⁻ cotransporter (NCC) in the early DCT. The Pvalb–/– mice showed increased diuresis and kaliuresis at baseline with higher aldosterone levels and lower lithium clearance. Acute furosemide administration increased diuresis and natriuresis/kaliuresis, but, surprisingly, did not increase calciuria in Pvalb–/– mice. NaCl supplementation of Pvalb–/– mice increased calciuria at baseline and after furosemide. The Pvalb–/– mice showed no significant diuretic response to hydrochlorothiazide, but an accentuated hypocalciuria. A decreased expression of NCC was detected in the early DCT of Pvalb–/– kidneys in the absence of ultrastructural and apoptotic changes. The PV-deficient mice had a positive Ca²⁺ balance and increased bone mineral density. Studies in mouse DCT cells showed that endogenous NCC expression is Ca²⁺-dependent and can be modulated by the levels of PV expression. These results suggest that PV regulates the expression of NCC by modulating intracellular Ca²⁺ signaling in response to ATP in DCT cells. They also provide insights into the Ca²⁺-sparing action of thiazides and the pathophysiology of distal tubulopathies.