A role of kidney K channel for acid-base regulation

肾脏通过尿酸排泄来调节血浆酸碱平衡。我们研究了TASK2，一种pH敏感的K通道，在重吸收HCO3-中的作用。用高灵敏的原位杂交技术发现，TASK2mRNA在肾近端小管中有表达，而在髓质粗大的升支和皮质集合管中无表达。有趣的是，小鼠PTS中TASK2的表达水平在0.28M NH4Cl6天后没有增加。TASK2 KO小鼠的体重较小(约15%)。饲喂正常饲料(pH：7.23+/-0.01)的KO小鼠，血浆pH呈轻度酸中毒。酸负荷后，WT小鼠血浆pH显著降低，而KO小鼠则无明显变化。提示KO小鼠的肾酸排泄系统和/或酸碱平衡系统可能被钝化，但酸负荷后其替代系统可能受到刺激。综上所述，这些结果有力地表明，TASK2可能是重吸收HCO3-在PT中以维持血浆酸碱平衡所必需的。

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.