Figure 8.
PTH-induced urinary cAMP, phosphate excretion, and cAMP formation in renal cortical tubule suspensions are impaired in AC6−/− mice. (A) Bolus application of PTH in WT mice dose-dependently increased fractional urinary Pi excretion and urinary cAMP excretion. In contrast to WT mice, the phosphaturic effect and cAMP formation in response to PTH are absent in AC6−/− mice. (B) Stimulation of cAMP formation by forskolin (Forsk; 10 µmol/L) or PTH is absent in freshly isolated renal cortical tubule suspensions of AC6−/− compared with WT mice. Protein concentration was adjusted to 60 µg/vial. Experiments were performed with phosphodiesterase inhibition (0.5 mmol/L 3-isobutyl-1-methylxanthine; n=6–8/genotype for clearance experiments and n=5/genotype for isolated cortical tubules). bw, body weight. *P<0.05 versus WT. #P<0.05 versus control same genotype.