Fig. 4

Pi increases murine PTH secretion via the CaSR. a Magnified mouse parathyroid gland before dissection in a 10-day-old control mouse. b Serum PTH levels measured from control and KO Casr mice before dissection. Data shown as median and min. to max. range (WT N = 11 and KO Casr N = 3). ^****P < 0.0001 by unpaired t test. c Effect of pathophysiologic Pi exposure at different Ca²⁺ concentrations on PTH secretion in freshly isolated parathyroid glands from 7- to 10-day-old control. WT glands (from four different litters) were sequentially exposed to normal Ca²⁺ (1.2 mM Ca²⁺; N = 11), low Ca²⁺ (0.8 mM Ca²⁺; N = 7 and 0.6 mM; N = 4), and high Ca²⁺ (1.6 mM Ca²⁺; N = 7). The KO Casr glands were exposed to 1.2, 0.8, and then 1.6 mM Ca²⁺ in turn (N = 3). PTH secretion measured every 30 min and normalized to baseline conditions (0.8 mM Pi/1.2 mM Ca²⁺) in the time course (left). For bar graphs, data normalized to 0.8 mM Pi at their respective Ca²⁺ concentration. Data shown as %mean ± SEM. ns not significant, ^*P < 0.05, ^**P < 0.01 by RM-ANOVA (Dunnett’s multiple comparison test). Source data are provided as a Source Data file