Kidney Week

Abstract: SA-PO1016

Parathyroid Hormone (PTH) Increases Paracellular Permeability to Na and Ca in the Cortical Thick Ascending Limb (CTAL)

Session Information

• Fluid and Electrolytes: Basic - II
  October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid and Electrolytes

• 901 Fluid and Electrolytes: Basic

Authors

• Prot-Bertoye, Caroline, INSERM, UMRS1138, Centre de Recherche des Cordeliers, Paris, France

Caroline Prot-Bertoye,

• Figueres, Lucile, INSERM, UMRS1138, Centre de Recherche des Cordeliers, Paris, France

Lucile Figueres,

• Ferriere, Elsa, INSERM, UMRS1138, Centre de Recherche des Cordeliers, Paris, France

Elsa Ferriere,

• Brideau, Gaëlle, CNRS- ERL8228 , Paris, France

Gaëlle Brideau,

• Breiderhoff, Tilman, Charité - Universitätsmedizin Berlin, Berlin, Germany

Tilman Breiderhoff,

• Müller, Dominik, Charité - Universitätsmedizin Berlin, Berlin, Germany

Dominik Müller,

• Houillier, Pascal, Paris Descartes University / INSERM, UMRS1138, Paris, France

Pascal Houillier,

Background

Ca absorption in the CTAL is passive along the paracellular pathway and requires the expression of claudin-16 at tight junction that increases the paracellular permeability to Ca (PCa). In vivo, Na is passively secreted along the paracellular pathway due to the transepithelial Na gradient, and to the permeability to Na of the tight junction that requires the expression of claudin-10b. In the CTAL, the lumen-positive transepithelial voltage (Vte) gradient that depends on claudin-10b expression and back diffusion of Na is critical for driving passive Ca reabsorption. PTH increases Ca transport across the CTAL but the mechanisms involved are imprecise.
We aim to elucidate if claudin-16, which determines PCa, and claudin-10b, which determines Vte and PNa, are involved in the effects of PTH on the CTAL and to identify the underlying mechanisms.

Methods

Murine CTAL were microperfused in vitro to measure transepithelial Ca and Na absorption under symmetrical conditions and ionic paracellular permeabilities under asymmetrical conditions with 0.1 mM furosemide in the lumen. All measures were made under control and experimental conditions. The ratio of permeabilities PNa/PCl was calculated according to the Goldman-Hodgkin-Katz equation.

Results

PTH (10^-10M) significantly increased Ca reabsorption in CTAL from claudin 16^+/+(+44 %) and claudin 16^-/-(+60 %) mice; Vte did not change, indicating that PTH increased PCa. PTH increased Na reabsorption (+15 %) and PNa/PCl (+22 %) in CTAL from wild type mice. Dibutyryl cAMP (5.10^-4M), ionomycin (10^-7M), thapsigargin (10^-6M), but not phorbol 12-Myristate 13-Acetate (10^-6M), significantly increased PNa/PCl. Dibutyryl cAMP and ionomycin had additive effects on PNa/PCl. H-89 (PKA inhibitor, 10^-5M) partly inhibited the effect of PTH on PNa/PCl.

Conclusion

We conclude that, in the mouse CTAL, PTH
- increases PCa independently of the presence of claudin-16
- increases PNa via cAMP- and cytosolic calcium-dependent signaling pathways.
Our results show that properties of intercellular tight junctions can be directly and rapidly controlled by intracellular signaling pathways in intact tissue.

Funding

• Government Support - Non-U.S.