Figure 6.

Sustained activation of with-no-lysine kinase (WNK)-STE20/SPS1-related proline-alanine-rich protein kinase (SPAK) by 5-day low-K⁺ diet (LK) blocks NaCl cotransporter (NCC) dephosphorylation by high-K⁺ gavage. C57/BL6 mice were fed with a low-K⁺ diet for either 1 day or 5 days. A: plasma K⁺ values in animals gavaged with K⁺ after 1 day (open circle) or 5 days of low-K⁺ diet control (Con; open square). Means and SDs are indicated by bars. B: phosphorylated (p)NCC, NCC, and β-actin from kidneys of mice gavaged after being fed a low-K⁺ diet for 1 day. Quantification is shown on the right. C: pNCC-to-NCC ratios for mice treated for 5 days with a low-K⁺ diet and gavaged with 3% of K⁺. Quantification is shown on the right. D: pNCC and NCC from mice fed with a low-K⁺ diet for 5 days and gavaged with 6% K⁺. Quantification is shown on the right. Means and SDs are indicated by bars. Data were compared using ANOVA with a Tukey’s post hoc test (A) or Mann–Whitney test (B − D). NS, not significant.