Fig. 1

Pathophysiologic concentrations of Pi significantly inhibit the CaSR. a Representative false-color images from epifluorescence imaging of Fura2-loaded CaSR-HEK cells showing CaSR-mediated \({\mathrm{Ca}}_i^{2 + }\) mobilization upon stimulation with increasing \({\mathrm{Ca}}_o^{2 + }\) concentrations (as indicated with warm colors). b–f Inhibitory effect of Pi on CaSR-mediated \({\mathrm{Ca}}_i^{2 + }\) mobilization upon stimulation with different concentrations of Ca²⁺ (b), and cotreatment with R568 (d, f), spermine (c), and cinacalcet (e). b, d, f (left) Representative \({\mathrm{Ca}}_i^{2 + }\) mobilization traces (Fura2 ratio) from a single cell in response to Pi (b, d), and time-matched buffer changes without Pi (f). f Inhibitory effect of Pi on CaSR-mediated \({\mathrm{Ca}}_i^{2 + }\) mobilization upon stimulation with R568 compared with time-matched control in the absence of Pi; data shown as %mean ± SEM. Data expressed as percent control of the area under the curve for each treatment, n = 7 (b), n = 10 (c), n = 11 (d), n = 9 (e), and n = 9 (f). Data shown in box-and-whisker plots: box ends indicate upper and lower quartiles; midline indicates the median while error bars indicate the range. Data were analyzed by using RM-ANOVA with Dunnett’s multiple comparison (b–e) or unpaired t test (f). ns not significant; *P < 0.05, **P < 0.01, and ***P < 0.001. Source data are provided as a Source Data file