Studies of catecholamine effect on cyclic AMP in human cultured thyroid cells: their interaction with thyrotrophin receptor
Toccafondi, R.S.; Brandi, M.L.; Rotella, C.M.; Zonefrati, R.
Acta Endocrinologica 102(1): 62-67
1983
ISSN/ISBN: 0001-5598 PMID: 6130662 Document Number: 218797
Even though adrenergic nerve terminals between and around thyroid follicles and catecholamine stimulation of thyroid adenylate cyclase were reported, there is no uniform concept of catecholamine interaction with TSH receptors. Therefore, the effect of catecholamines on TSH-stimulated cAMP accumulation in human follicular thyroid cells was investigated, thus eliminating the extrathyroidal actions of catecholamines. Epinephrine, norepinephrine and isoproterenol appeared to be rapid and potent stimulators of intracellular cAMP accumulation, the half maximum increase doses being 4 .times. 10-7 M, 1 .times. 10-5 M and 5 .times. 10-7 M, respectively. While propranolol (1 .times. 10-5 M) prevented the stimulatory effect of catecholamines and failed to inhibit the effect of bovine TSH, phentolamine (1 .times. 10-5 M) enhanced the potency of norepinephrine and bovine TSH, leaving that of epinephrine unchanged. The effects of epinephrine (2 .times. 10-8 M) and isoproterenol (2 .times. 10-8 M) were additive to that of bovine TSH (0.5 mU/ml), but the effect of simultaneous stimulation with norepinephrine (5 .times. 10-7 M) and bovine TSH (0.5 mU/ml) was lower than expected. Prenalterol, a selective .beta.1-agonist, did not stimulate cAMP accumulation, while terbutaline, a selective .beta.2-agonist, exerted a potent stimulation. Metoprolol, a selective .beta.1-adrenergic blocker, did not affect the response of thyroid follicular cells to isoproterenol. These results demonstrate the existence of .beta.-adrenergic receptors in human thyroid follicular cells, mainly of the .beta.2 type, apparently not correlated with TSH receptors. The existence of .alpha.-adrenergic receptors which counter-regulate TSH functional responses in human thyroid follicular cells is suggested.