Kidney Week

Abstract: PO1079

Furosemide Alleviates Hypercalciuria and Hypomagnesemia in Claudin 16-Deficient Mice

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Basic
  November 04, 2021 | Location: On-Demand, Virtual Only
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid, Electrolyte, and Acid-Base Disorders

• 901 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

• Kriuchkova, Natalia, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Natalia Kriuchkova,

• Breiderhoff, Tilman, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Tilman Breiderhoff,

• Müller, Dominik, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Dominik Müller,

• Yilmaz, Duygu Elif, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Duygu Elif Yilmaz,

• Bachmann, Sebastian, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Sebastian Bachmann,

• Mutig, Kerim, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Kerim Mutig,

Background

Loss-of-function mutations in the CLDN16 gene encoding for claudin-16 lead to Familial Hypomagnesaemia with Hypercalciuria and Nephrocalcinosis (FHHNC) in human. Claudin-16 resides in tight junctions of the thick ascending limb (TAL) and mediates paracellular reabsorption of divalent cations. The ensuing distal convoluted tubule (DCT), connecting tubule (CNT) and cortical collecting duct (CCD) perform transcellular Ca²⁺ and Mg²⁺ reabsorption via the transient receptor potential (TRP) channels, TRPV5 and TRPM6. DCT, CNT, and CCD exhibit unique functional and structural plasticity enabling them to compensate for defects of proximal salt reabsorption. Using claudin-16-deficient (Cldn16-/-) mice as a FHHNC model, we tested the hypothesis that enforcement of distal nephron function using a loop diuretic furosemide may enhance the transcellular reabsorption of Ca²⁺ and Mg²⁺ thus compensating for the paracellular TAL defect.

Methods

Wild-type (WT) vs. Cldn16-/- mice were treated with furosemide (50 mg/kg body weight) for 7 days followed by physiological, morphological and biochemical evaluation of kidneys.

Results

Compared to WT, Cldn16-/- mice showed significantly increased urinary excretion of Ca²⁺ and Mg²⁺ and hypomagnesemia at baseline. Furosemide enhanced urinary Ca²⁺ excretion without concomitant increase of urinary Mg²⁺ levels in WT. In contrast, Cldn16-deficient mice responded to the diuretic with a marked reduction of urinary Ca²⁺ levels and normalization of plasma Mg²⁺ levels. Evaluation of distal Ca²⁺ and Mg²⁺ transport proteins by immunoblotting and immunofluorescence showed furosemide-dependent increases of TRPV5 and calbindin levels in Cldn16-/- kidneys along with signs of hyperthrophy of the distal nephron.

Conclusion

The present results suggest that loop diuretics bear potential to alleviate symptoms of Cldn16-deficiency due to compensatory stimulation of electrolyte reabsorption in DCT, CNT, and CCD.

Funding

• Government Support – Non-U.S.