Thiazide-induced hypocalciuria is accompanied by a decreased expression of Ca2+ transport proteins in kidney.

Details

Serval ID
serval:BIB_26653
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Thiazide-induced hypocalciuria is accompanied by a decreased expression of Ca2+ transport proteins in kidney.
Journal
Kidney International
Author(s)
Nijenhuis T., Hoenderop J.G., Loffing J., van der Kemp A.W., van Os C.H., Bindels R.J.
ISSN
0085-2538
Publication state
Published
Issued date
2003
Volume
64
Number
2
Pages
555-564
Language
english
Abstract
INTRODUCTION: Thiazide diuretics have the unique characteristic of increasing renal Na+ excretion, while decreasing Ca2+ excretion. However, the molecular mechanism responsible for this thiazide-induced hypocalciuria remains unclear. The present study investigates the effect of thiazides on the expression of the proteins involved in active Ca2+ transport as well as the role of extracellular volume (ECV) status. METHODS: Hydrochlorothiazide (HCTZ), 12 mg/24 hours, was administered during 7 days to Wistar rats by osmotic minipumps. In addition, ECV contraction was either prevented by Na+ repletion or induced by a low-salt diet. Expression levels of the proteins involved in active Ca2+ transport [i.e., epithelial Ca2+ channel (TRPV5/ECaC1), calbindin-D28K, Na+/Ca2+ exchanger (NCX1)], as well as the thiazide-sensitive Na+ Cl- cotransporter (NCC) were determined by real-time quantitative polymerase chain reaction (PCR) and semiquantitative immunohistochemistry. RESULTS: HCTZ significantly reduced urinary Ca2+ excretion (22%+/- 5% relative to controls). Hematocrit was significantly increased, confirming ECV contraction. In addition, Na+ depletion virtually abolished Ca2+ excretion (8%+/- 1%), while Na+ repletion during HCTZ treatment prevented both ECV contraction and hypocalciuria. HCTZ significantly decreased mRNA expression of TRPV5 (71%+/- 6%), calbindin-D28K (53%+/- 6%), NCX1 (51%+/- 8%) and NCC (50%+/- 11%), regardless of ECV status or calciuresis. Immunohistochemistry revealed reduced TRPV5 (43%+/- 2%), calbindin-D28K (59%+/- 1%) and NCC (56%+/- 4%) abundance. Furthermore, during HCTZ treatment, the subset of tubules coexpressing NCC and calbindin-D28K was significantly reduced (43%+/- 5%) and a disturbed cellular localization of NCC was observed. CONCLUSION: These data suggest that ECV contraction is a critical determinant of the thiazide-induced hypocalciuria, which is accompanied by a decreased expression of Ca2+ transport proteins.
Keywords
Animals, Calcium, Calcium Channels, Diuretics, Electrolytes, Hydrochlorothiazide, Immunoblotting, Immunohistochemistry, Kidney, Male, Polymerase Chain Reaction, Rats, Rats, Wistar, Sodium, Sodium Chloride Symporter Inhibitors, Sodium Chloride Symporters, Sodium-Calcium Exchanger, Symporters, TRPV Cation Channels
Pubmed
Web of science
Open Access
Yes
Create date
19/11/2007 12:23
Last modification date
20/08/2019 13:05
Usage data