Influence of lithium carbonate on the thyrotropin receptor in vitro.

Thyroid tissues excised from 5 patients with Graves' disease were used to study the influence of lithium carbonate on the thyrotropin (TSH) receptor in vitro by cAMP generation assay and TSH binding to its receptor. Lithium carbonate was able to decrease the cAMP production of the crude thyroid plasma membranes stimulated by TSH at concentrations of 6mM and higher. However, lithium carbonate had no effect on 5'-guanylylimidodiphosphate-induced cAMP production in thyroid plasma membranes up to concentrations of 10mM. Lithium carbonate was able to decrease the binding of 125I-TSH to crude thyroid plasma membranes at concentrations of 6mM and higher. It decreased the binding of 125I-TSH to solubilized TSH receptor at concentrations of 6mM and higher. These findings suggest that lithium carbonate can influence the TSH receptor in vitro and may be one of the action mechanisms of lithium on the thyroid gland.