Fig. 6. Proposed model for location bias in cAMP and PTHR pharmacology.

Upon basolateral stimulation of proximal tubule kidney cells, the PTHR-generated endosomal cAMP pool ensures increases in serum Vitamin D by inducing the expression of 1-α(OH)ase, the rate-limiting hydroxylase catalyzing the formation of active Vitamin D, which subsequently stimulates an increase in serum Ca²⁺. The PTHR-generated plasma membrane cAMP pool might contribute to the inhibition of phosphate import, presumably by increasing endocytosis of the Na⁺-dependent phosphate cotransporter 2A (NPT2A).