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

AUTOR(ES)

Zhou, Yuehan

FONTE

National Academy of Sciences

RESUMO

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]BL of 5% and a fixed pHBL of 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]BL from 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 pHBL of 7.40, caused JHCO3 to rise 2.5-fold but did not significantly affect JV. Finally, increasing pHBL from 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]BL of 5%, did not affect either JHCO3 or JV. Analysis of the JHCO3 and JV data implies that, as the tubule alters JHCO3, it compensates the reabsorption of other solutes to keep JV approximately constant. Because the cells cannot respond acutely to pH changes, we propose that the responses of JHCO3 and 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]BL involve 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.

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