WT Cx26 hemichannels are also permeable to Ca²⁺. (A and B) Currents from oocytes expressing G45E (A) and WT Cx26 (B) recorded 24 and 48 h after injection of RNA. At 48 h, recordings are shown in 1.8 and 5.0 mM extracellular Ca²⁺. Voltage step protocols are the same as in Fig. 3 A. At 48 h, oocytes expressing G45E show larger hemichannel currents in 1.8 Ca²⁺ (compared with 24 h) along with larger Ca²⁺-activated Cl currents. Upon raising Ca²⁺ to 5 mM, G45E hemichannels continued to activate at positive voltages and to induce Ca²⁺-activated Cl currents. With increased expression of WT Cx26 hemichannels, Ca²⁺-activated Cl currents were also induced, albeit more weakly in comparison to G45E. (C) Peak chloride current is plotted as a function of the membrane conductance. Measurements were obtained from the same voltage protocol as shown in A and B). The magnitude of the chloride current was measured at the peak that developed at −110 mV after the activating voltages steps. Baseline was taken as the instantaneous current upon stepping to −110 mV that preceded the development of the large inward transient. The membrane conductance was measured at the end of the activating voltage step, the bulk of which was caused by hemichannel activation. Open symbols are data from WT Cx26, and closed symbols are from G45E. Experiments from individual oocytes are plotted as different symbol shapes. Lines represent fits (by eye) to the data for illustration purposes. n = 8 oocytes for G45E, and n = 9 oocytes for WT Cx26.