Proximal renal tubular acidosis in TASK2 K+ channel-deficient mice reveals a mechanism for stabilizing bicarbonate transport

The acid- and volume-sensitive TASK2 K + channel is strongly expressed in renal proximal tubules and papillary collecting ducts. This study was aimed at investigating the role of TASK2 in renal bicarbonate reabsorption by using the task2 –/– mouse as a model. After backcross to C57BL6, task2 –/– mice showed an increased perinatal mortality and, in adulthood, a reduced body weight and arterial blood pressure. Patch-clamp experiments on proximal tubular cells indicated that TASK2 was activated during \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{HCO}}_{3}^{-}\end{equation*}\end{document} transport. In control inulin clearance measurements, task2 –/– mice showed normal NaCl and water excretion. During i.v. NaHCO 3 perfusion, however, renal Na + and water reabsorption capacity was reduced in –/– animals. In conscious task2 –/– mice, blood pH, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{HCO}}_{3}^{-}\end{equation*}\end{document} concentration, and systemic base excess were reduced but urinary pH and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{HCO}}_{3}^{-}\end{equation*}\end{document} were increased. These data suggest that task2 –/– mice exhibit metabolic acidosis caused by renal loss of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{HCO}}_{3}^{-}\end{equation*}\end{document} . Both in vitro and in vivo results demonstrate the specific coupling of TASK2 activity to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{HCO}}_{3}^{-}\end{equation*}\end{document} transport through external alkalinization. The consequences of the task2 gene inactivation in mice are reminiscent of the clinical manifestations seen in human proximal renal tubular acidosis syndrome.