Intracellular pH changes during oligodendrocyte differentiation in primary culture.

We have studied the characteristics of pH(i) regulation at different stages of rat oligodendrocyte differentiation in primary culture. pH(i) was measured at 37 degrees C using the pH-sensitive fluorescent probe BCECF. In immature oligodendrocyte progenitor (OLP), three distinct ionic mechanisms were involved in pH(i) regulation: (i) a sodium-independent Cl(-)/HCO(-)(3) exchanger, (ii) a Na(+)/H(+) exchanger and (iii) a voltage-dependent Na(+)-HCO(-)(3) cotransporter. The two latter mechanisms were also detected in more differentiated pro-oligodendrocytes and in mature oligodendrocytes whereas the Cl(-)/HCO(-)(3) exchanger was not active in these two later stages of differentiation. The presence of this Cl(-)/HCO(-)(3) exchanger (that acts as a chronic acidifying mechanism) only in immature OLP maintains in these cells a steady-state pH(i) value significantly lower than values measured in more differentiated cells. The possible involvement of this pH(i) change in triggering cell differentiation is discussed. Copyright 2000 Wiley-Liss, Inc.