Evidence from renal proximal tubules that \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} and solute reabsorption are acutely regulated not by pH but by basolateral \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} and CO2
Authors: Zhou Yuehan , Zhao Jinhua , Bouyer Patrice , Boron Walter F. 
Published: February 2005

Respiratory acidosis, a decrease in blood pH caused by a rise in [CO2], rapidly triggers a compensatory response in which the kidney markedly increases its secretion of H+from blood to urine. However, in this and other acid-base disturbances, the equilibrium CO2+ H2O ⇄\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}+ H+makes it impossible to determine whether the critical parameter is [CO2],\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}, and/or pH. Here, we used out-of-equilibrium\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{CO}}_{2}/{\mathrm{HCO}}_{3}^{-}\end{equation*}\end{document}solutions to alter basolateral (BL)\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}, [CO2], or pH, systematically and one at a time, on isolated perfused S2 rabbit proximal tubules. We found that increasing\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}^{-}]_{{\mathrm{BL}}}\end{equation*}\end{document}from 0 to 44 mM, at a fixed [CO2]BLof 5% and a fixed pHBLof 7.40, caused\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}reabsorption (JHCO3) to fall by half but did not significantly affect volume reabsorption (JV). Increasing [CO2]BLfrom 0% to 20%, at a fixed\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}^{-}]_{{\mathrm{BL}}}\end{equation*}\end{document}of 22 mM and pHBLof 7.40, causedJHCO3to rise 2.5-fold but did not significantly affectJV. Finally, increasing pHBLfrom 6.80 to 8.00, at a fixed\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}^{-}]_{{\mathrm{BL}}}\end{equation*}\end{document}of 22 mM and [CO2]BLof 5%, did not affect eitherJHCO3orJV. Analysis of theJHCO3andJVdata implies that, as the tubule altersJHCO3, it compensates the reabsorption of other solutes to keepJVapproximately constant. Because the cells cannot respond acutely to pH changes, we propose that the responses ofJHCO3and the reabsorption of other solutes to changes in\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}^{-}]_{{\mathrm{BL}}}\end{equation*}\end{document}or [CO2]BLinvolve sensors for basolateral\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}and CO2.