Effects of iodide on thyroid follicle structure and electrophysiological potentials of cultured thyroid cells

In cultured porcine thyroid cells, exposure to iodide induces morphological and electrophysiological changes in the cells and suppresses the iodine uptake and organification activities of the cells. NaI affects thyroid structures: after exposure to 10(-7), 10(-6), and 10(-5) M NaI, the follicles first lose their typical roundness, and then the numbers of microvilli decrease. NaI (10(-6) and 10(-5) M) decreases the thyroid electrical membrane potentials. NaI induces suppression of iodine uptake and organification: exposure to 10(-6) and 10(-5) M NaI suppresses subsequently determined iodine uptake and organification. This iodide-induced suppression of iodine uptake and organification may be related to the iodide-induced morphological and electrophysiological changes. The iodide-induced changes and suppression of iodide uptake and organification are reversible. They are observed when thyroid cells are cultured in the presence of TSH.