Figure 4. Comparing the effect on pH_i of Ca²⁺ and H⁺ injections in an EGTA-loaded cell.

The cell was injected with EGTA (by a current of 10 nA for 2 min) before the start of the record shown. After 3 injections of Ca²⁺, the EGTA electrode was withdrawn and normal Hepes-buffered Ringer was replaced briefly by bicarbonate-buffered Ringer to accelerate pH_i recovery. Then an HCl microelectrode was inserted and used to make 4 injections of H⁺. Bicarbonate Ringer was again used to accelerate pH_i recovery.