Influence of lithium on cell function in two different cell systems.

Lithium is widely used in the treatment and prophylaxis of bipolar psychiatric disorders. It accumulates in the thyroid gland and can cause goitre or thyroid dysfunction. The mechanisms of various effects of the lithium ion on thyroid cells have not been completely clarified. The aim of our work was to establish whether lithium, in the presence or absence of TSH, stimulates the synthesis of cAMP; as model systems we used a strain of rat thyroid follicular cells FRTL-5 and a line of Chinese hamster ovary fibroblasts with the human TSH receptor (CHO-R). Lithium at concentrations of 0.35 mM, 1 mM, 1.4 mM, 1.7 mM and 2 mM without TSH and at selected concentrations with TSH stimulation significantly increased cAMP synthesis in FRTL-5 and in CHO-R cells when compared with controls without lithium. These results are different from the published data, which have been unable to confirm the influence of lithium on cAMP synthesis or have even reported the inhibition of cAMP synthesis. However, in most published investigations only lithium in combination with TSH was tested. In conclusion, lithium was found to stimulate cAMP synthesis in FRTL-5 cells and in CHO-R cells.