(A) Calcium mobilization of primary trachea epithelial cells isolated from mice in response to 670 μM ITA or 100 μM ATP, as determined by Fluo-4AM assay. (B) Tracheas were cultured ex vivo, and cilia beating–derived fluid flow was monitored by tracing fluorescent bead movement under the microscope. The trajectory of 20 individual beads in 1 minute with or without 500 μM ITA is shown. Scale bar: 150 μm. (C) Quantification of bead movement speed in trachea culture from individual Oxgr1^+/+ (n = 3) and Oxgr1^–/– (n = 3) mice in the presence of 500 μM ITA or 100 μM ATP. Each dot represents an independent biological replicate. *P < 0.05 and **P < 0.01, by paired, 2-tailed Student’s t test. (D) Primary human bronchial epithelium cells were infected by a control lentivirus (Vec) or viruses expressing sgRNAs targeting OXGR1 (sgOXGR1). Calcium mobilization in response to 500 μM ITA was determined by Fluo-4AM assay. (E and F) Comparison of bead movement speed between ALI culture of human bronchial epithelium cells in the presence of 500 μM ITA or 100 μM ATP. **P < 0.01 and ****P < 0.0001, by 1-way ANOVA (E) or unpaired, 2-tailed Student’s t test (F). Data indicate the mean ± SEM. (G–I) Anesthetized mice of the indicated genotype (n = 4–6 per group) were intranasally administered PBS or 500 μM ITA, and their nasal cavities were harvested 1 hour after ITA administration. (G) Sections were taken from the most proximal aspect of the nasal cavities. (H) Representative images of Alcian blue/PAS staining of nasal cavities are shown. (I) Quantification of mucin-containing cells in the indicated groups of animals. ****P < 0.0001, by 2-tailed Student’s t test. Data indicate the mean ± SEM.