Intracellular pH regulation in rat Schwann cells

We examined H + and HCO 3 − transport mechanisms that are involved in the regulation of intracellular pH of Schwann cells. Primary cultures of Schwann cells were prepared from the sciatic nerves of 1–3‐day‐old rats. pH i of single cells attached to cover slips was continuously monitored by measuring the absorbance spectra of the pH‐sensitive dye dimethylcarboxyfluorescein incorporated intracellularly. The average pH i of neonatal Schwann cells bathed in HEPES mammalian solution was 7.17 ± 0.02 (n = 32). In the nominal absence of HCO 3 − , pH i spontaneously recovered from an acute acid load induced by exposing the Schwann cells to 20 mM NH 4 + (NH 4 + prepulse). This pH i recovery from the acute acid load was totally inhibited in the absence of external Na + or in the presence of 1 mM amiloride. In both cases, the pH i recovery was readily restored upon readdition of external Na + or removal of amiloride. In the steady‐state, addition of amiloride caused a small and slow decrease in pH i which was readily reversed upon removal of amiloride. In the presence of HCO 3 − , removal of external Cl‐ caused pH i to rapidly and reversibly increase by 0.23 = 0.03 (n = 15) and the initial rate of alkalinization was 20.6 ± 2.7 × 10‐4 pH/sec. In the absence of external Na + , removal of bath Cl − still caused pH i to increase by 0.15 ± 0.02 and the initial rate of pH i increase was not significantly altered. In the nominal absence of HCO 3 − , removal of bath Cl‐ caused pH i to increase very slightly (0.05 ± 0.01) with an initial dpH i /dt of only 4.4 ± 0.2 × 10 −4 pH/sec (n = 4). Addition of 100 μM DIDS did not inhibit the pH i increase caused by removal of bath Cl − . These data indicate that (1) Rat Schwann cells regulate their pH i via an Na‐H exchange mechanism which is moderately active at steady‐state pH i . (2) In the presence of HCO 3 − , there is a Na‐independent Cl‐HCO 3 (base) exchanger which also contributes to regulation of intracellular pH in Schwann cells. © 1994 Wiley‐Liss, Inc.