Effect of Cd²⁺ on WT CFTR channels. (A and B) Responses of WT cysless channels to 5 µM or 1 mM intracellular Cd²⁺ in inside-out patches. Dashed lines mark the zero current levels (also applicable to all figures). (C) Comparison of effects of intracellular Cd²⁺ on WT cysless CFTR channels. Numbers in parentheses indicate the number of data points (also applicable to all figures). Mean ± SEM is shown. (D) 1 mM Cd²⁺ applied from the extracellular side did not alter whole-cell forskolin-activated CFTR currents.