On the role of bicarbonate as a hydrogen ion buffer in rat CNS neurones

The role of bicarbonate as a hydrogen ion buffer has been investigated using the fluorescent dye BCECF in individual rat cerebellar, hippocampal and neocortical neurones maintained in culture. The steady-state intracellular pH (pHi) was estimated to be 7.07 +/- 0.05 (n = 22) in CO2-HCO3(-)-buffered media. Buffering power (beta) estimated from the addition and removal of weak bases was ca 10 mM (pH unit)-1 and was found to be similar in both CO2-HCO3(-)- and Hepes-buffered media. The membrane-permeant carbonic anhydrase inhibitor, acetazolamide (10-20 microM), did not affect estimates of beta. The results indicate that CO2-HCO3- does not act as an open buffer system in these neurones.