Figure 4.

Calcium and gadolinium ions block mutant Cx43 hemichannel activity. Oocytes expressing Cx43 mutations were sequentially stepped from −70 mV to +20 mV (a) while being perfused with medium containing 2 mM Ca²⁺, 0.2 mM Ca²⁺, or 5 µM Gd³⁺ (b). In the example shown for a Cx43-E227D expressing cell (c), hemichannel currents were initially suppressed by 2 mM Ca²⁺, and increased markedly when the extracellular calcium was reduced to 0.2 mM. Hemichannel currents were also suppressed by perfusion with 5 µM Gd³⁺, and recovered rapidly when Gd³⁺ was washed out with 0.2 mM Ca²⁺. Currents were suppressed again by increasing the extracellular calcium to 2.0 mM.