Voltage-dependent Na(+)-HCO3- cotransporter and Na+/H+ exchanger are involved in intracellular pH regulation of cultured mature rat cerebellar oligodendrocytes.
Intracellular pH (pHi) was measured at 37 degrees C in mature rat cerebellar oligodendrocytes dissociated in culture by using the pH-sensitive probe BCECF. Cells were identified by anti-galactocerebroside antibody. The mean steady-state pHi was 7.02 in the absence of CO2/bicarbonate (Hepes-buffered solution) at an external pH of 7.40 and 7.04 in 5% CO2/25 mM bicarbonate-buffered solution at the same external pH; this value was modified neither by the removal of external chloride nor by the addition of the chloride-coupled transport blocker DIDS. In both external solutions steady-state pHi values were strongly dependent on external pH. In Hepes-buffered solution pHi recovery following an acid load required external Na+ and was completely inhibited by amiloride, indicating the presence of a Na+/H+ exchanger. In CO2/bicarbonate-buffered solution amiloride partially reduced the pHi recovery rate, indicating the presence of a bicarbonate-dependent pHi regulating mechanism. Membrane depolarization induced by increasing external K+ concentration elicited an alkalinization only in the presence of external Na+ and bicarbonate. Analysis of the calculated HCO3- fluxes with respect to membrane potential indicated that these fluxes were mediated by a Na(+)-HCO3- cotransport with a stoichiometry of 1:3. These results demonstrate that a Na+/H+ exchanger and a Na(+)-HCO3- cotransporter are involved in pHi regulation of mature oligodendrocytes.
Boussouf
A
A
Laboratoire de Neurobiologie Cellulaire, CNRS, Centre de Neurochimie, Strasbourg, France.
Lambert
R C
RC
Gaillard
S
S
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001639:Bicarbonates / Q000378:metabolism / Q000494:pharmacology; D002021:Buffers; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D016922:Cellular Senescence / Q000502:physiology; D002531:Cerebellum / Q000166:cytology; D002712:Chlorides / Q000378:metabolism / Q000494:pharmacology; D004232:Diuretics / Q000494:pharmacology; D004558:Electric Stimulation; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006531:HEPES; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D015640:Ion Channel Gating / Q000502:physiology; D009836:Oligodendroglia / Q000737:chemistry* / Q000166:cytology / Q000502:physiology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D027982:Sodium-Bicarbonate Symporters; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
D001639:Bicarbonates; D002021:Buffers; D002352:Carrier Proteins; D002712:Chlorides; D004232:Diuretics; D005452:Fluoresceins; D005456:Fluorescent Dyes; D027982:Sodium-Bicarbonate Symporters; D017923:Sodium-Hydrogen Exchangers; D011189:Potassium Chloride; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D012964:Sodium; D006531:HEPES