ISSN:
1432-2013
Keywords:
Rabbit renal proximal tubule
;
S3 segment
;
Basolateral cell membrane-Cl−/HCO3 − exchange
;
Cell buffer capacity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Isolated microperfused S3 segments of rabbit renal proximal tubule were investigated with pH-sensitive double-barrelled intracellular microelectrodes to determine whether the Cl−/base exchanger, which we have previously identified in the basolateral cell membrane of this segment requires HCO3 − or can also work in CO2/HCO3 − free conditions. Cell pH (pHi) was measured in response to sudden substitution of bath Cl− by gluconate. In control solutions containing 25 mmol/l HCO3 pHi increased initially by 5.0±0.3 × 10−3 unit/s but after perfusion with CO2/HCO3 −-free solutions pHi of the same cells increased only by 1.3±0.2 × 10−3 unit/s in response to Cl− substitution. From measurements of the cellular buffering power it was calculated that the control base flux had fallen drastically from 3.7±0.3 to 0.3±0.1 × 10−12 mols/s·cm tubule length. To test whether the remaining flux might have resulted from metabolic CO2, oxidative metabolism was poisoned with cyanide (5 mmol/l). This abolished the pH change (ΔpHi) in CO2/HCO3 −-free solutions, but did not affect the pH shift in the presence of HCO3 −. The data indicate that basolateral Cl−/base exchange in S3 segment requires HCO3 − to operate. A model in which HCO3 − absorption proceeds in form of OH− and CO2 can be largely excluded.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00370766
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