The mechanism of basolateral membrane base transport was examined in the in vitro microperfused rabbit proximal convoluted tubule (PCT) in the absence and presence of ambient CO2/HCO3- by means of the microfluorometric measurement of cell pH. The buffer capacity of the cells measured using rapid NH3 washout was 42.8 +/- 5.6 mmol.liter-1.pH unit-1 in the absence and 84.6 +/- 7.3 mmol.liter-1.pH unit-1 in the presence of CO2/HCO3-. In the presence of CO2/HCO3-, lowering peritubular pH from 7.4 to 6.8 acidified the cell by 0.30 pH units and lowering peritubular Na from 147 to 0 mM acidified the cell by 0.25 pH units. Both effects were inhibited by peritubular 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate (SITS). In the absence of exogenous CO2/HCO3-, lowering peritubular pH from 7.4 to 6.8 acidified the cell by 0.25 pH units and lowering peritubular Na from 147 to 0 mM decreased cell pH by 0.20 pH units. Lowering bath pH from 7.4 to 6.8 induced a proton flux of 643 +/- 51 pmol.mm-1.min-1 in the presence of exogenous CO2/HCO3- and 223 +/- 27 pmol.mm-1.min-1 in its absence. Lowering bath Na from 147 to 0 mM induced proton fluxes of 596 +/- 77 pmol.mm-1.min-1 in its absence. The cell acidification induced by lowering bath pH or bath Na in the absence of CO2/HCO3- was inhibited by peritubular SITS or by acetazolamide, whereas peritubular amiloride had no effect. In the absence of exogenous CO2/HCO3-, cyanide blocked the cell acidification induced by bath Na removal, but was without effect in the presence of exogenous CO2/HCO3-. We reached the following conclusions. (a) The basolateral Na/base n greater than 1 cotransporter in the rabbit PCT has an absolute requirement for CO2/HCO3-. (b) In spite of this CO2 dependence, in the absence of exogenous CO2/HCO3-, metabolically produced CO2/HCO3- is sufficient to keep the transporter running at 30% of its control rate in the presence of ambient CO2/HCO3-. (c) There is no apparent amiloride-sensitive Na/H antiporter on the basolateral membrane of the rabbit PCT.
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1 December 1987
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December 01 1987
Basolateral membrane Na/base cotransport is dependent on CO2/HCO3 in the proximal convoluted tubule.
R Krapf,
R Krapf
Department of Medicine, University of California, San Francisco 94143.
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R J Alpern,
R J Alpern
Department of Medicine, University of California, San Francisco 94143.
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F C Rector, Jr,
F C Rector, Jr
Department of Medicine, University of California, San Francisco 94143.
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C A Berry
C A Berry
Department of Medicine, University of California, San Francisco 94143.
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R Krapf
Department of Medicine, University of California, San Francisco 94143.
R J Alpern
Department of Medicine, University of California, San Francisco 94143.
F C Rector, Jr
Department of Medicine, University of California, San Francisco 94143.
C A Berry
Department of Medicine, University of California, San Francisco 94143.
Online ISSN: 1540-7748
Print ISSN: 0022-1295
J Gen Physiol (1987) 90 (6): 833–853.
Citation
R Krapf, R J Alpern, F C Rector, C A Berry; Basolateral membrane Na/base cotransport is dependent on CO2/HCO3 in the proximal convoluted tubule.. J Gen Physiol 1 December 1987; 90 (6): 833–853. doi: https://doi.org/10.1085/jgp.90.6.833
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