THE INFLUENCE OF CALCIUM ON THYROID FOLLICULAR CELLS FRTL-5 IN-VITRO

The present work is based on the results of in vivo experiments on rat s, which had shown that hypercalcemia had led to morphological and bio chemical hyperfunction of thyroid follicular cells, The regulation of the activity of follicular cells should directly, or indirectly via pa racrine action of serotonin secreted from parafollicular cells, depend on the presence of calcium ions. The effect of calcium was studied on a cell line of rat follicular cells FRTL-5 (Fischer Rat Thyroid cells in Low serum) using three methods: measuring the quantity of produced cAMP (cyclic adenosine 3',5'-monophosphate), measuring [H-3]thymidine incorporation into cell DNA and transmission electron microscopy, Res ults show that calcium has no effect on cAMP production. Calcium at 1. 3 mM, 3 mM 10 mM, 20 mM and 30 mM concentrations increases [H-3]thymid ine incorporation into cell DNA when compared with controls without ca lcium, Calcium at the concentration of 30 mM has no effect on FRTL-5 c ell morphology, TSH (thyrotropin) stimulates follicular cells; at high er extracellular concentrations (3 mM, 10 mM, 20 mM, 30 mM), calcium d iminishes its effect, presumably by activation of a cAMP phosphodieste rase which disintegrates cAMP and/or by inhibition of adenyl cyclase.