ISSN:
1437-7799
Keywords:
Key words Microperfusion
;
Alkalosis
;
Electrophysiology
;
Potassium
;
HEPES buffer
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Background. Clinically, it is well known that alkalosis induces hypokdemia, but the precise mechanisms of these interactions between acid-base disturbances and potassium homeostasis are not known with certainty. The role of intracellular alkalosis in the regulation of transepithelial potassium transport was examined in rabbit cortical collecting ducts (CCD). Methods. Intracellular alkalosis was induced by 25 mM N-2 hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES) buffer in which bicarbonate and CO2 were eliminated. Intracellular pH (pHi) was measured by the load of 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) dye in principal cells. Isolated CCD was perfused in vitro, and electrophysiological studies and electrolyte transport studies were performed with or without HEPES buffer. Results. Basal pHi in the Krebs-Ringer-Bicarbonate solution was 7.11 ± 0.06. Alkalization by HEPES buffer solution (pH 7.4) resulted in pHi 7.54 ± 0.16. Intracellular alkalization induced by HEPES solution significantly hyperpolarized transepithelial voltage, while net potassium flux increased from −17.3 ± 3.6 to −21.0 ± 3.4 pmol·min−1·mm−1. However, lumen-to-bath isotope sodium flux did not change. The basolateral membrane voltage of the principal cells increased from −74.6 ± 3.0 to −79.6 ± 2.9 mV and transepithelial resistance decreased significantly from 113.1 ± 2.7 to 100.9 ± 20.1 Ω·cm2. The calculated fractional resistance of the apical membrane decreased, indicating that intracellular alkalosis increases apical potassium conductance. In the presence of either basolateral ouabain, luminal amiloride, or luminal barium, the HEPES-induced hyperpolarization was preserved. Conclusion. The present study demonstrates that intracellular pH is an important determinant of apical potassium conductance in CCD. Additionally, it should be noted that in the experiments using HEPES buffer solution, intracellular pH in certain epithelial cells was alkalinized by the elimination of bicarbonate and CO2.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s101570050014
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