Altered ion homeostasis due to impaired CFTR function in CF neutrophils. Intracellular levels of (A) Cl⁻, (C) Na⁺, and (E) Mg²⁺ in neutrophils from HCs, patients with CF of the ΔF508/ΔF508 (CFΔ) or G551D/ΔF508 genotype following ivacaftor treatment (CFG+iva), and HC cells treated with CFTRinh-172 (10 μM; Inh) were analyzed using electron probe X-ray microanalysis. Relative values of CFΔ or Inh normalized to HC or CFG+iva, respectively, are shown on the left y-axis and are related to recorded ion concentrations in cytosols of HC cells on the right y-axis.^35,36  (A) Cytosolic Cl⁻ was increased in CFΔ or inhibitor-treated cells (P = .006 between HC and CFΔ and P = .005 between CFG+iva and Inh, Student t test, n = 3 subjects per group). Na⁺ was also increased in these samples (P = .006 between HC and CFΔ and P = .0001 between CFG+iva and Inh, Student t test, n = 3 subjects per group). Mg²⁺ levels were decreased in CFΔ and Inh treated cells (P = .04 between HC and CFΔ and P = .04 between CFG+iva and Inh, Student t test, n=3 subjects per group). (B,D,F) Relative changes in cytosolic (B) Cl⁻, (D) Na⁺, and (F) Mg²⁺ levels in CFTRinh-172 (10 μM) treated HC neutrophils compared with vehicle control (0.05% v/v DMSO) treated cells were measured for 16 minutes using MQAE, SBFI-AM, and Mag-Fluo-4-AM, respectively (P = .0001, paired Student t test, n = 3 subjects per group). All measurement are mean ± SEM from biological replicates.