Proton currents in resting and activated VSOP/Hv1^−/− neutrophils. (A and B) Typical currents recorded in blood neutrophils from WT and VSOP/Hv1^−/− mice, using the whole-cell configuration and acidic pipette solutions to activate proton channels (pHi/o = 6.1/7.2). Proton currents were elicited by 3.5-s depolarizing steps ranging from −80 to +80 mV, applied every 20 s from a holding potential of −60 mV. (C) Current–voltage relationship of time-dependent outward currents recorded in 5 WT and 18 VSOP/Hv1^−/− blood neutrophils. (D and E) Effect of 100 nM PMA on the currents recorded at +60 mV in the perforated patch configuration (pHi/o = 7.0/7.0). The lack of proton currents in VSOP/Hv1^−/− cells persisted after application of PMA to activate the phagocyte NADPH oxidase. Arrowheads in D show the PMA-activated current. The dashed line indicates zero current level. (F) Mean current amplitude at +60mV before and after PMA addition. Data are mean values ± SEM of 9 WT and 18 VSOP/Hv1^−/− neutrophils that were tested in 27 independent experiments. ***, P < 0.0001, unpaired Student's t test. Five WT and nine VSOP/Hv1^−/− mice were used for these experiments.