Beta-adrenergic stimulation of cyclic AMP content and parathyroid hormone release from isolated bovine parathyroid...

The effects of beta-adrenergic agonists and antagonists on cyclic AMP (cAMP) accumulation and parathyroid hormone (PTH) release from isolated bovine parathyroid cells have been determined. Beta-adrenergic agonists markedly stimulate cAMP production and PTH release with an order of potency (-) isoproterenol greater than (-)epinephrine greater than greater than (-) norepinephrine, suggesting a beta2-type adrenergically mediated process. Both effects are blocked by the beta-blocker propranolol with the strict stereospecificity expected for a beta-adrenergic response. Low calcium concentrations also stimulate cAMP accumulation, but the cyclic nucleotide response under these conditions is only 3% of that obtained with isoproterenol, raising the possibility that factors other than cAMP may control low calcium-mediated PTH release. The release of PTH by low calcium is also not blocked by propranolol, confirming the independence of the response to low ambient calcium from the beta-adrenergic receptor. These studies substantiate further the utility of the isolated parathyroid cell preparation for studying secretagogue-mediated alterations in cyclic nucleotides and hormone secretion. Isolated cells also also make feasible the direct identification of beta-adrenergic receptors in parathyroid cell membranes and whole cells.