Premium
Islet‐activating protein discriminates between different inhibitors of thyroidal cyclic AMP system
Author(s) -
Cochaux P.,
Van Sande J.,
Dumont J.E.
Publication year - 1985
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(85)80539-1
Subject(s) - medicine , endocrinology , cyclase , chemistry , phosphodiesterase , iodide , adenylate kinase , norepinephrine , phosphodiesterase inhibitor , muscarinic acetylcholine receptor , receptor , enzyme , biology , biochemistry , dopamine , organic chemistry
TSH‐induced cyclic AMP accumulation in dog thyroid slices is inhibited by norepinephrine through an α 2 ‐adrenergic receptor, by carbamylcholine through a muscarinic cholinergic receptor, and by iodide. The inhibitory effect of iodide bears on the adenylate cyclase, but the exact mechanism of its action is still unknown. It is known that norepinephrine acts through activation of the N 1 subunit of the cyclase, and that carbamylcholine, activating a phosphodiesterase, acts independently of N i IAP (islet‐activating protein) has been shown to inactivate the N i subunit. We studied the effect of IAP on the inhibitory action of iodide, norepinephrine, and carbamylcholine on cyclic AMP accumulation in TSH‐stimulated thyroid slices. Incubations of 15 or 22 h, and relatively high concentrations of IAP (250 ) were necessary to demonstrate an effect of IAP on thyroid slices. We report here that, under those conditions, inhibition of cyclic AMP accumulation by norepinephrine, but not by carbamylcholine or iodide, was suppressed by IAP treatment. These results indicate that the cyclase inhibition by iodide, is either not mediated by N i or if mediated by N i involves a mode of regulation of this coupling protein that is different from that by which the other 'N i ‐mediated' inhibitory hormones act on the enzyme.