Voltage-dependent Na+-HCO3− cotransporter and Na+/H+ exchanger are involved in intracellular pH regulation of cultured mature rat cerebellar oligodendrocytes
✍ Scribed by Abdelhamid Boussouf; Regis C. Lambert; Stephane Gaillard
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 197 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0894-1491
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✦ Synopsis
Intracellular pH (pH i ) was measured at 37°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 pH i was 7.02 in the absence of CO 2 /bicarbonate (Hepes-buffered solution) at an external pH of 7.40 and 7.04 in 5% CO 2 /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 pH i values were strongly dependent on external pH. In Hepes-buffered solution pH i recovery following an acid load required external Na 1 and was completely inhibited by amiloride, indicating the presence of a Na 1 /H 1 exchanger. In CO 2 /bicarbonate-buffered solution amiloride partially reduced the pHi recovery rate, indicating the presence of a bicarbonatedependent pH i regulating mechanism. Membrane depolarization induced by increasing external K 1 concentration elicited an alkalinization only in the presence of external Na 1 and bicarbonate. Analysis of the calculated HCO 3 2 fluxes with respect to membrane potential indicated that these fluxes were mediated by a Na 1 -HCO 3 2 cotransport with a stoichiometry of 1:3. These results demonstrate that a Na 1 /H 1 exchanger and a Na 1 -HCO 3 2 cotransporter are involved in pH i regulation of mature oligodendrocytes.