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Research Article Free access | 10.1172/JCI114092

Contributions of cellular leak pathways to net NaHCO3 and NaCl absorption.

P A Preisig and R J Alpern

Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-9030.

Find articles by Preisig, P. in: JCI | PubMed | Google Scholar

Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-9030.

Find articles by Alpern, R. in: JCI | PubMed | Google Scholar

Published June 1, 1989 - More info

Published in Volume 83, Issue 6 on June 1, 1989
J Clin Invest. 1989;83(6):1859–1867. https://doi.org/10.1172/JCI114092.
© 1989 The American Society for Clinical Investigation
Published June 1, 1989 - Version history
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Abstract

Proton and formic acid permeabilities were measured in the in vivo microperfused rat proximal convoluted tubule by examining the effect on intracellular pH when [H] and/or [formic acid] were rapidly changed in the luminal or peritubular fluids. Apical and basolateral membrane H permeabilities were 0.52 +/- 0.07 and 0.67 +/- 0.18 cm/s, respectively. Using these permeabilities we calculate that proton backleak from the luminal fluid to cell does not contribute significantly to net proton secretion in the early proximal tubule, but may contribute in the late proximal tubule. Apical and basolateral membrane formic acid permeabilities measured at extracellular pH 6.62 were 4.6 +/- 0.5 X 10(-2) and 6.8 +/- 1.5 X 10(-2) cm/s, respectively. Control studies demonstrated that the formic acid permeabilities were not underestimated by either the simultaneous movement of formate into the cell or the efflux of formic acid across the opposite membrane. The measured apical membrane formic acid permeability is too small to support all of transcellular NaCl absorption in the rat by a mechanism that involves Na/H-Cl/formate transporters operating in parallel with formic acid nonionic diffusion.

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