Calcium handling in VSOP/Hv1^−/− neutrophils. Changes in cytosolic Ca²⁺ were measured with fura-2. (A) SOCE in blood neutrophils exposed to PMA for 20 min to activate the oxidase. Cells were deprived of Ca²⁺, treated with 1 µM thapsigargin to deplete Ca²⁺ stores, and exposed to 2 mM Ca²⁺ to reveal SOCE. Traces are means of 9 WT and 14 VSOP/Hv1^−/− recordings (>10 cells each) from five WT and three VSOP/Hv1^−/− mice. (B and C) Calcium elevations evoked by 10 µM fMIVIL in bone marrow neutrophils pretreated or not with PMA. Traces in B are means of 19 and 64 cells measured in five and seven independent experiments from four WT and four VSOP/Hv1^−/− mice. Traces in C are means of four separate recordings (>10 cells each) from two WT and two VSOP/Hv1^−/− mice. The chemotactic peptide was added at t = 0 (arrows). (D) Mean changes in cytosolic Ca²⁺ evoked by fMIVIL (area under the curve, AUC) and by Ca²⁺ readmission (Δ ratio amplitude). Data are means ± SD of the experiments in A–C. **, P < 0.001; *, P < 0.05, unpaired Student's t test.