A proton pump contributes to neuroblastoma x glioma cell membrane potentials.
The contribution of an electrogenic proton pump to the membrane potential of neuroblastoma x glioma hybrid NG 108-15 cells was determined with whole-cell voltage and current recordings and cell volume measurements with the preparation bathed in symmetrical 140 mM KCl solutions. The effects of the K+ channel blockers tetraethylammonium and 4-aminopyridine and of the H+-ATPase inhibitor bafilomycin A1 on the membrane potential and input resistance revealed that the membrane potential is generated by an outward H+ pump current of 5-15 pA in equilibrium with an inward passive current. This conclusion is supported by both current- and voltage-clamp results obtained when the preparation was bathed in a Na+-containing external solution after K+ channel blockade with Cs+ in the pipette. Additional support was obtained by measurement of the volume of cells incubated in solutions containing 140 mM KCl. Tetraethylammonium induced a bafilomycin-sensitive increase in inward K+ current and an increase in cell volume of 76% which we believe to be a consequence of the K+ influx. Finally, comparison of membrane potentials obtained in experiments using Na+-containing external, and K+-containing pipette solutions and after K+ channel blockade with Cs+ in the pipette also showed that, under normal physiological conditions, the resting membrane potential is essentially determined by an electrogenic H+ pump.
Rouzaire-Dubois
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Laboratoire de Neurobiologie cellulaire et moléculaire, CNRS, F-91198 Gif-sur-Yvette Cedex, France.
Dubois
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JM
D002462:Cell Membrane / Q000502:physiology; D004553:Electric Conductivity; D005910:Glioma / Q000473:pathology*; D006822:Hybrid Cells / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D009447:Neuroblastoma / Q000473:pathology*; D018408:Patch-Clamp Techniques; D017494:Proton Pumps / Q000502:physiology*; D014407:Tumor Cells, Cultured / Q000502:physiology
D017494:Proton Pumps