Norepinephrine and thyrotropin effects on the thyroid in vitro: simultaneous stimulation of iodide organification and antagonism of thyroxine release

Endocrinology
M L MaayanA From

Abstract

Norepinephrine (NE), which has previously been shown to inhibit TSH-induced T4 release by mouse thyroids in vitro, was found to stimulate iodide organification. The concentration of NE (6 X 10(-7) M) necessary to stimulate organification of iodide was 10 times less than the concentration (6 X 10(-6) M) required for inhibition of TSH-induced T4 release. Both actions of NE were exerted through an alpha-adrenergic receptor, since they were inhibited by phentolamine but not by l-propranolol. One milliunit of TSH maximally stimulated T4 release only, but larger amounts (100 mU) also stimulated organification. TSH stimulation of T4 release and organification was not affected by adrenergic antagonists and therefore was not mediated by adrenergic receptors. N6, O2-Dibutyryl cAMP and isobutylmethylxanthine, like TSH, stimulated T4 release. Their actions were inhibited by NE. However, both compounds, unlike TSH, failed to enhance organification in mouse thyroids. The effects of TSH and NE on the cAMP content of incubated mouse thyroids were also studied. TSH induced a prolonged increase in thyroidal cAMP during the 90-min incubation; this increase was unaffected by alpha- or beta-adrenergic antagonists. In contrast, NE (6 X 10(-5) M) pro...Continue Reading

Citations

Sep 1, 1987·Biulleten' eksperimental'noĭ biologii i meditsiny·S N RiashchikovA A Zelenin
Sep 3, 1984·European Journal of Pharmacology·B HayeC Jacquemin
Dec 1, 1985·Proceedings of the National Academy of Sciences of the United States of America·D Corda, L D Kohn
Jan 1, 1987·Endocrine Research·M L MaayanA F Debons

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