[The stimulation by calcium of the thyroidal iodine metabolism fits into the scheme of "stimulus-secretion coupling" (author's transl)].
In vivo, in the rat, in nutritional experiments, calcium accelerated iodine entry into the thyroid and augmented the concentration of iodine in the gland (1). These data are compatible with the hypothesis of Ca2+ acting on the thyroid as in "stimulus-secretion coupling" where the cation promotes extrusion of the contents of exocytotic granules (2). The whole set of experimental data from the in vivo work (1, 3) fit into the view that Ca2+ might increase the velocity of iodine entry into and the concentration of iodine in the thyroid by promoting exo cytosis of non iodinated thyroglobulin; and so do data from in vitro experiments in the literature, provided the statement: "Ca2+ is required for the in vitro TSH stimulation of 131I transfer from the intrathyroidal iodide pool into thyroglobulin" (5) is inverted into: "Ca2+ is required for the TSH stimulation of the transfer of Tg into the sites of its iodination"; these are located in the lumen of the follicle (4). The transfer of Tg (= exocytosis) was shown to be limiting factor to the acceleration of iodine binding by TSH, in vivo (6).
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D007455:Iodine / Q000378:metabolism*; D051381:Rats; D013954:Thyroglobulin / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism; D013972:Thyrotropin / Q000494:pharmacology
D013972:Thyrotropin; D013954:Thyroglobulin; D007455:Iodine; D002118:Calcium
La stimulation par le calcium du métabolisme thyroïdien de l'iode est compatible avec le schéma du "stimulus secretion coupling".