STK39 and Hypokalemia: In contrast, the increased in pNCC did not occur in the SPAK-KI mice treated with aldosterone, despite a similar reduction in plasma potassium, supporting, as has been previously shown, that with no lysine kinase/STE20-proline alanine-rich kinase (WNK/SPAK) pathway is also required to achieve the NCC phosphorylation due to hypokalemia [19,20].