Abstract: TH-OR020
TRPV5-Driven Distal Reabsorption Contributes to Hypocalciuria in Sodium-Chloride Cotransporter Blockade
Session Information
- Fluids and Electrolytes: Bench and Bedside
November 06, 2025 | Location: Room 361A, Convention Center
Abstract Time: 04:40 PM - 04:50 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic
Authors
- Bahena-López, Jessica Paola, Oregon Health & Science University, Portland, Oregon, United States
- Reyes, Jeremiah V., Oregon Health & Science University, Portland, Oregon, United States
- Su, Xiao-Tong, Oregon Health & Science University, Portland, Oregon, United States
- Yang, Chao-Ling, Oregon Health & Science University, Portland, Oregon, United States
- Demirci, Hasan, Ankara Yildirim Beyazit Universitesi Tip Fakultesi, Ankara, Turkey
- Bachmann, Sebastian, Charite - Universitatsmedizin Berlin, Berlin, BE, Germany
- McCormick, James A., Oregon Health & Science University, Portland, Oregon, United States
- Nelson, Jonathan W., University of Southern California, Los Angeles, California, United States
- Ellison, David H., Oregon Health & Science University, Portland, Oregon, United States
Background
Inhibition of the thiazide-sensitive sodium-chloride cotransporter (NCC) can lead to hypokalemia, hypomagnesemia, metabolic alkalosis, and notably, hypocalciuria. The hypocalciuric effect of thiazides underlies their use in preventing recurrent calcium-containing kidney stones. Enhanced proximal calcium reabsorption is often suggested as the predominant mechanism of thiazide-induced hypocalciuria, but the role of distal calcium reabsorption remains debated. To address, we integrated transcriptomics and morphometric analyses with assessment of TRPV5-mediated distal calcium transport.
Methods
C57BL/6 and Calbindin-Cre-INTACT (Isolation of Nuclei TAgged in specific Cell Types) male mice were treated with metolazone (MTZ; 50 mg/kg/day via chow) for 4 days to inhibit NCC. After 4 days, C57BL/6 mice received a single dose of gentamicin to acutely inhibit TRPV5-mediated calcium transport as described by Dimke (PMID: 35022312). Kidneys from Calbindin-Cre-INTACT mice were used to enrich distal cells for single nuclei-RNA sequencing using 10x Genomics.
Results
MTZ-treated mice exhibited reduced urinary calcium excretion compared to controls, consistent with NCC inhibition. MTZ treatment led to a reduction in distal convoluted tubule (DCT) 1 cell abundance but increases in connecting tubule (CNT), collecting duct, intercalated and proliferative cell populations. Hypertrophy of the calcium-transporting CNT was documented morphologically. Using a previously described calcium score to assess calcium transport capacity (PMID: 38238903), we found that calcium handling was primarily localized to DCT2 and CNT. In MTZ-treated mice, the calcium score remained unchanged in DCT2 but was reduced in CNT, likely owing to diminished distal calcium delivery and consistent with prior reports. Surprisingly, gentamicin challenge revealed higher TRPV5-dependent fractional calcium reabsorption in MTZ-treated mice than controls.
Conclusion
Hypocalciuria following NCC inhibition results not only from enhanced proximal calcium reabsorption, but also from increased distal calcium transport. This distal component is supported by CNT hypertrophy, preserved DCT2 identity, and TRPV5-mediated reabsorption, underscoring the critical role of distal calcium handling in this adaptive response.
Funding
- NIDDK Support