Bicarbonate sensing in mouse cortical astrocytes during extracellular acid/base disturbances.

Key Points: The present study suggests that the electrogenic sodium-bicarbonate cotransporter, NBCe1, supported by carbonic anhydrase II, CAII, provides an efficient mechanism of bicarbonate sensing in cortical astrocytes. This mechanism is proposed to play a major role in setting the pH responses to extracellular acid/base challenges in astrocytes. A decrease in extracellular [HCO ] during isocapnic acidosis and isohydric hypocapnia, or an increase in intracellular [HCO ] during hypercapnic acidosis, was effectively sensed by NBCe1, which carried bicarbonate out of the cells under these conditions, and caused an acidification and sodium fall in WT astrocytes, but not in NBCe1-knockout astrocytes.