Figure 4. Effects of external Cd²⁺ and Cu-Phen on mutant I227C.

(A) Representative traces recorded from an oocyte expressing I227C and bathed in ND96 without (w/o) prior incubation with 100 µM DTT (1 hour at 20°C) and without Cd²⁺ or Cu-Phen; Currents were evoked as in Figure 2. (B) Oocytes expressing I227C channels were first pre-incubated with 100 µM DTT (1 hour at 20°C) and subsequently washed with ND96 in the absence or presence of 100 µM CdCl₂. (C) Same as in B but with 100 µM Cu-Phen. Shown are representative traces and current-voltage relations that were determined as indicated. (D) Representative traces of an oocyte expressing mutant I227C, bathed in ND96 containing 100 µM Cu-Phen and subsequently washed with either ND96 (left panel) or ND96 containing 1 mM DTT (right panel). Currents were evoked by a step depolarization from −80 mV to +30 mV. Similar results have been obtained in 6 other cells. (E) Representative traces of an oocyte expressing I227C, preincubated for 10 min with 100 µM Cu-Phen at −80 mV and then washed out for 5 min with ND96 at −80 mV. Currents were then evoked either by a depolarizing step to 0 mV (red trace) or by a hyperpolarizing step to −140 mV (black trace), after which a fast re-application of Cu-Phen was applied (red or black trace after the arrow). Similar results have been obtained in 5 other cells.