FIGURE 2.

The outward current is carried by Cl^– and is insensitive to Zn²⁺. (A) Superimposed human neutrophil whole-cell currents in response to depolarising voltage ramps (from –136 to +84 mV) at 36 s (black trace) and 270 s (blue trace) after breakthrough. A steady state level of outward current was then attained which is not affected by Zn²⁺ 100 μM (red trace) but depends on external Cl^– (green trace). The inset focuses on the change of reversal that accompanies the substitution of external Cl^– for gluconate. (B) Superimposed responses to stepped voltage pulses (from –96 mV to –136, –76, –36, +4, +44 and +84 mV, respectively, from bottom to top traces) in control conditions after full development of the emerging outward current. (C) Time course of outwardly rectifying Cl^– current increase in 14 human neutrophils at +84 mV under iso-osmotic conditions. Inset: very minimal current was recorded in perforated whole cell conditions. (D) Time course of plasma membrane hyperpolarizations (ΔIo) in 14 human neutrophils (the same cells as C) after the development of the outwardly rectifying Cl^– current under iso-osmotic conditions. All experiments were carried out using solution set B (Table 1).