Figure 9. pH-dependent modulation of g_j in HeLa cells expressing wild-type Cx57 and untagged EGFP.

A, intracellular alkalization with NH₄Cl (5 mm) increased g_j from ∼0.2 nS to ∼8 nS. MKR solution containing 2 mm of CaCl₂ was used in this experiment. g_j was measured by applying repeated V_j ramps of ±20 mV. The inset shows I_j responses to V_j ramps during an initial period of NH₄Cl application. I_j responses to positive and negative ∼70 mV voltage steps show moderate (∼25%) decay. B, I_j trace measured in response to 60 s long V_j ramps from 0 to −100 mV shows well expressed V_j-gating under control conditions at pH_{pipette−sol}= 7.3, while under exposure to NH₄Cl, the I_j–V_j relationship is almost linear indicating almost no V_j-gating.