Iodide modulation of Ca2+ efflux from mouse thyroid.
In a preceding report, we showed evidence that thyrotropin (TSH) stimulates Ca2+ efflux from mouse thyroid gland and that TSH stimulation of Ca2+ efflux is inhibited by acute administration of excess iodide to mice fed a low iodine diet (Hashizume et al., 1984). The observations suggested that iodide inhibits Ca2+ efflux through an inhibition of TSH-sensitive adenylate cyclase activity. We found further, that iodide inhibits dibutyryl cyclic AMP (DBC)-stimulated Ca2+ efflux. The results suggested that iodide influences the step subsequent to the generation of cyclic AMP. In this report, we studied whether iodide can inhibit Ca2+ efflux by a mechanism which is distinct from adenylate cyclase inhibition. The acute administration of excess iodide to mice fed a regular diet did not decrease the basal Ca2+ efflux rate in the thyroid. TSH-induced stimulation of Ca2+ efflux in thyroids obtained from regular diet-treated mice was not modified by iodide administration. Iodide injection to mice fed a low iodide diet, however, decreased the basal Ca2+ efflux rate though the content of cyclic AMP in the thyroids was not altered by this treatment. The decreased-Ca2+ efflux rate induced by iodide in the low iodine diet-treated thyroids was not modified by TSH in vitro. The results indicate that an acute administration of excess iodide in thyroid inhibits Ca2+ efflux not only by an inhibition of adenylate cyclase but also by an inhibitory action which is distinct from the adenylate cyclase inhibiting action of iodide.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D004032:Diet; D007454:Iodides / Q000494:pharmacology*; D008297:Male; D051379:Mice; D012974:Sodium Iodide / Q000494:pharmacology; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology
D007454:Iodides; D013972:Thyrotropin; D000242:Cyclic AMP; D012974:Sodium Iodide; D002118:Calcium