Fig. 5. Basolateral actions of PTH and its variants in polarized MDCK cells.

(A and B) Representative western blot (A) and quantification (B) of 1-α(OH)ase relative to GAPDH in polarized PTHR-expressing MDCK cells after basolateral stimulation with either LA-PTH, PTH^WT, or PTH^7D for 8 hours. Graph shows individual data points and means ± SD. P values were determined by one-way ANOVA with Tukey test. The P value for untreated vs PTH^7d is 0.25.

(C) Quantification of cAMP responses in polarized MDCK cells expressing the Green cADDis sensor at t = 30 min after basolateral stimulation with 100 nM PTH^WT, LA-PTH, or PTH^7d. Percentage of cAMP responses is relative to the response in the presence of forskolin (Fsk). Data are means ± SD from n = 90–107 cells.

(D) cAMP time courses in polarized MDCK cells following addition of 100 nM LA-PTH or PTH^7d in the absence or presence of 1 μM D-Trp¹²,Tyr³⁴-bPTH_7–34, a cell-impermeable competitive antagonist at the basolateral membrane. Horizontal bars indicate the application of ligand and antagonist. Data are means ± SEM from n = 48 cells.