A role of kidney K channel for acid-base regulation

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The kidney regulates plasma acid-base balance by urinary excretion of acid. We investigated roles of TASK2, pH-sensitive K channel, for reabsorption of HCO3-. By using a high sensitive ISH, we found that TASK2 mRNA was expressed in kidney proximal tubules (PT), but not in the medullary thick ascending limb or the cortical collecting duct. Interestingly, the level of TASK2 expression in mice PTs was not increased after application of 0.28 M NH4Cl for 6 days. TASK2 KO mice were smaller (about 15%) in weight. Plasma pH showed weak acidosis in KO mice fed normal chow (pH: 7.23+/-0.01). After acid loading, plasma pH in WT mice significantly decreased, but not in KO mice. This suggests that renal acid excretion system and/or acid-base balance system may be blunted in KO mice, but their alternative system may be stimulated upon acid-loading. In conclusion, these results strongly suggest that TASK2 may be essential for reabsorption of HCO3- in PT to maintain plasma acid-base balance.