Electrogenic Na‐independent HCO3transport in OK cells

Enrique Pastoriza‐Munoz; Fuling Hsiang; Mark Graber

摘要

AbstractWe have shown previously that OK cells recover from an acid load in a medium nominally CO2‐free by extruding H via a Na/H exchanger and a passive H‐conductive pathway. In this work, the regulation of cell pH (pHi) was studied after additon or withdrawal of CO2/HCO3(5CO2, 95 mM HCO3, pH = 8) using the fluoroprobe BCECF. In the presence of Na and amiloride to inhibit Na/H exchange, the recovery of pHiafter CO2entry and CO2exit were found to depend in part on HCO3entry and exit, respectively. Efflux of H per se also contributed to restoring pHiafter CO2addition, whereas H influx may have played a smaller role to normalize pHiafter CO2removal. DIDS, 0.5mM, significantly inhibited both recovery phases of pHi. Removal of Na failed to inhibit the recovery of pHiafter CO2addition and removal. Cl removal also failed to inhibit pHirecovery after CO2removal. Cell depolarization in the presence of Na moderately stimulated the pHirecovery rate after CO2addition whereas it markedly inhibited the normalization of pHiafter CO2removal. Cell depolarization in the absence of sodium had only a slight effect to increase pHirecovery after CO2addition but markedly prevented the pHirecovery after CO2removal. These results indicate that OK cells lack Na or Cl‐dependent HCO3transport systems. The OK cell possesses a novel stilbene‐sensitive electrogenic HCO3transport system that is involved in the regulation of cell pH. © 1992 Wiley

Electrogenic Na‐independent HCO3transport in OK cells

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