[Effect of lithium on iodide uptake and DNA synthesis in porcine thyroid cells in culture].

We investigated the direct effect of lithium on porcine thyroid cells in culture to exclude the secondary regulatory factors. First we have studied the effect of lithium on TSH-induced iodide uptake. Significant suppression was seen at 0.1 mmol/1 and half-maximal suppression was obtained at the pharmacological concentration reported in serum of patients. The suppression was dose-dependent and reversible. Besides the suppression of cAMP production stimulated by TSH, lithium also inhibited iodide uptake stimulated by forskolin or 8 bromo-cAMP. These results demonstrated that lithium inhibits TSH-induced iodide uptake not only by reducing cAMP production but also by affecting the post cAMP production process. Next we studied the effect of lithium on DNA synthesis of the cultured porcine thyroid cells. Lithium stimulated [3H] thymidine incorporation of the thyroid cells in the basal condition (0.5% fetal calf serum), and with IGF-I (100 micrograms/l) added it stimulated incorporation further. The minimal concentration for the significant increase was 0.5 mmol/l and 0.1 mmol/l, respectively. These results suggested that lithium might contribute to the formation of the goiter directly at the cellular levels in patients treated with agent.