Characterization of the β-Adrenergic Receptor Mediating Secretion of Parathyroid Hormone

Summary

In vitro incubation studies with bovine parathyroid gland slices compared the relative responsiveness of parathyroid hormone (PTH) secretion to isoproterenol, epinephrine or norepinephrine. Isoproterenol was the most potent and norepinephrine the least potent of the three stimuli, suggesting a β₂ type of an adrenergic response. However in this in vitro system, tazalol, a selective β₁ adrenergic agonist significantly stimulated PTH secretion, whereas terbutaline, a selective β₂ agonist had no effect. In addition, practolol, a selective β₁ adrenergic antagonist blocked isoproterenol- or tazolol-stimulated PTH secretion. In vivo studies in normal human subjects showed that injection of the nonselective β agonist, isoproterenol, (0.15 mg s.c.) significantly increased, whereas injection of the selective β₂ agonist, terbulatine (0.3 mg s.c.) had no effect on serum PTH levels. These latter studies with putative selective β adrenergic agents suggest that the β adrenergic receptor mediating PTH secretion is of the β₁ type (in contrast to the studies above with nonselective agents). The studies suggest that the β adrenergic receptor mediating PTH secretion apparently differs from the classical β₁ receptor described in the myocardium or the classical β₂ receptor described in the bronchial smooth muscle.

Key-Words

Parathyroid Hormone - β-Adrenergic Receptor - Selective β-Adrenergic Agents