Intracellular pH regulation in rat Schwann cells

AbstractWe examined H+ and HCO3− 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. pHi 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 pHi of neonatal Schwann cells bathed in HEPES mammalian solution was 7.17 ± 0.02 (n = 32). In the nominal absence of HCO3−, pHi spontaneously recovered from an acute acid load induced by exposing the Schwann cells to 20 mM NH4+ (NH4+ prepulse). This pHi 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 pHi 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 pHi which was readily reversed upon removal of amiloride. In the presence of HCO3−, removal of external Cl‐ caused pHi 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 pHi to increase by 0.15 ± 0.02 and the initial rate of pHi increase was not significantly altered. In the nominal absence of HCO3−, removal of bath Cl‐ caused pHi to increase very slightly (0.05 ± 0.01) with an initial dpHi/dt of only 4.4 ± 0.2 × 10−4 pH/sec (n = 4). Addition of 100 μM DIDS did not inhibit the pHi increase caused by removal of bath Cl−. These data indicate that (1) Rat Schwann cells regulate their pHi via an Na‐H exchange mechanism which is moderately active at steady‐state pHi. (2) In the presence of HCO3−, there is a Na‐independent Cl‐HCO3 (base) exchanger which also contributes to regulation of intracellular pH in Schwann cells. © 1994 Wiley‐Liss, Inc.