HUMAN THYROID EPITHELIAL-CELLS CULTURED IN MONOLAYERS .2. INFLUENCE OF SERUM ON THYROGLOBULIN AND CAMP PRODUCTION

An in vitro system of secondary cultures of human thyroid follicular e pithelial cells in monolayer is described. The 72-h influence of serum and six supplements (thyrotropin. insulin, somatostatin: transferrin, hydrocortisone. glycyl-histidyl-lysine acetate) on growth and functio n in presence of 3-isobutyl-L-methyl-xanthine (IBMX) was investigated. The function of the cells was evaluated by production of the second m essenger adenylate cyclase (cAMP) and the end product thyroglobulin (T g). Growth was measured as the H-3-thymidine uptake of the cells. Thre e days of TSH-depletion preceeded the experiments. In presence of IBMX TSH stimulated cAMP production, while stimulation of Tg was only pres ent in some cultures. In absence of IBMX TSH always stimulated the Tg production. The stimulation was independent of the presence of the oth er five investigated nutritional factors in physiological concentratio ns. TSH in concentrations from 0.1-10 U/1 stimulated the 72ih H-3-thym idine uptake of the cells. The TSH-stimulated production of Tg and cAM P decreased significantly with increasing concentrations of fetal calf serum (0-10%), (t = 0.49, P < 0.001, n = 6-29 and t = 0.75, P < 0.001 , n = 6-29, respectively). Thus, serum as a complex, variable and not fully characterized mixture of hormones and growth factors was crucial to the attachment of the cells to the substrate, but inhibited differ entiated functions of the human thyroid cells.