Increased colonic K + excretion through inhibition of the H,K-ATPase type 2 helps reduce plasma K + level in a murine model of nephronic reduction

Hyperkalemia is frequently observed in patients at the end-stage of chronic kidney disease (CKD), and has possible harmful consequences on cardiac function. Many strategies are currently used to manage hyperkalemia, one consisting of increasing fecal K + excretion through the administration of cation-exchange resins. In this study, we explored another more specific method of increasing intestinal K + secretion by inhibiting the H,K-ATPase type 2 (HKA2), which is the main colonic K + reabsorptive pathway. We hypothetised that the absence of this pump could impede the increase of plasma K + levels following nephronic reduction (N5/6) by favoring fecal K + secretion. In N5/6 WT and HKA2KO mice under normal K + intake, the plasma K + level remained within the normal range, however, a load of K + induced strong hyperkalemia in N5/6 WT mice (9.1 ± 0.5 mM), which was significantly less pronounced in N5/6 HKA2KO mice (7.9 ± 0.4 mM, p < 0.01). This was correlated to a higher capacity of HKA2KO mice to excrete K + in their feces. The absence of HKA2 also increased fecal Na + excretion by inhibiting its colonic ENaC-dependent absorption. We also showed that angiotensin-converting-enzyme inhibitor like enalapril, used to treat hypertension during CKD, induced a less severe hyperkalemia in N5/6 HKA2KO than in N5/6 WT mice. This study therefore provides the proof of concept that the targeted inhibition of HKA2 could be a specific therapeutic maneuver to reduce plasma K + levels in CKD patients.