Figure 4. Effect of HOE 694 in the absence and presence of HCO3 -/CO2 . The application of the HCO3 - buffer itself induced a transient acidification presumably due to the high permeability of CO2. Vice versa, removal of HCO3 -/CO2 strongly alkalinized the cells. The recovery from the alkaline load had a much slower time course than the recovery from acid load..