Abstract: TH-OR076

Role of ClC-K and Barttin in Low-Potassium Induced Sodium-Chloride Cotransporter Activation and Hypertension in Mouse Kidney

Session Information

Category: Fluid, Electrolytes, and Acid-Base

  • 703 Na+, K+, Cl- Basic

Authors

  • Nomura, Naohiro, Tokyo Medical and Dental University, Tokyo, Japan
  • Shoda, Wakana, Tokyo Medical and Dental University, Tokyo, Japan
  • Wang, Yuanlong, Tokyo Medical and Dental University, Tokyo, Japan
  • Takahashi, Daiei, Tokyo Medical and Dental University, Tokyo, Japan
  • Zeniya, Moko, Tokyo Medical and Dental University, Tokyo, Japan
  • Sohara, Eisei, Tokyo Medical and Dental University, Tokyo, Japan
  • Rai, Tatemitsu, Tokyo Medical and Dental University, Tokyo, Japan
  • Uchida, Shinichi, Tokyo Medical and Dental University, Tokyo, Japan
Background

The sodium-chloride cotransporter (NCC) was identified as a key molecule regulating potassium balance. The mechanisms of NCC regulation during low extracellular potassium concentrations have been investigated in vitro showing that the hyperpolarization induced by low potassium concentrations increased chloride efflux through the ClC-K chloride channels, leading to the activation of chloride-sensitive WNK kinases and their downstream molecules including SPAK and NCC. However, this mechanism was not investigated in vivo.

Methods

We used the barttin hypomorphic mouse (Bsndneo/neo mice), expressing very low levels of barttin and ClC-K channels since barttin is an essential ß-subunit of ClC-K. Mice were fed a normal diet or a low-potassium diet in vivo. Kidney slices were incubated in different potassium concentration buffer ex vivo. Then, SPAK and NCC phosphorylation was evaluated by Western blotting.

Results

In contrast to Bsnd-/- mice, Bsndneo/neo mice survived to adulthood, which enabled us to investigate the role of ClC-K in NCC activation. When mice were fed a normal diet, there was no significant difference in total and phosphorylated NCC between wild-type mice and Bsndneo/neo mice. In Bsndneo/neo mice, SPAK and NCC activation (phosphorylation) after consuming a high-salt and low-potassium (HSLK) diet was clearly impaired compared to that in wild-type mice. In ex vivo kidney slice experiment, the increase in phosphorylated NCC in low-potassium medium was also blunted in Bsndneo/neo mice. Furthermore, the increase in blood pressure was observed in wild-type mice fed a HSLK diet, which was not evident in the Bsndneo/neo mice.

Conclusion

Our study provides in vivo evidence that ClC-K and barttin play important roles in the activation of the WNK4-SPAK-NCC cascade and the blood pressure regulation, in response to a low-potassium diet.

Funding

  • Government Support - Non-U.S.