Characterisation of the cyclic AMP response to thyrotrophin in monolayer cultures of normal human thyroid cells

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Abstract
The cAMP response to thyrotropin (TSH) was investigated in cells prepared from human thyroid tissue obtained during surgery for subtotal laryngectomy and maintained under in vitro conditions as primary monolayer cultures. When cells were incubated with 1.0 mU TSH/ml, a maximal level of intracellular cAMP was reached after 20 min of incubation in the presence of 0.5 mM 3-isobutyl-1-methyl xanthine (MIX). This level of cAMP was sustained for at least 2 h. Half-maximal stimulation of cAMP was produced by TSH doses of 1-5 mU/ml. In a study of a series of 8 groups of monolayer cultures, each derived from a single, different thyroid gland, the mean stimulation of cAMP given by 50 mU TSH/ml was 37.8-fold greater than in non-stimulated cell monolayers. Significant stimulation to 50 .mu.U TSH/ml was observed in some monolayers and the precision of measurement of TSH was better than 15% over the TSH dose range 0.2-1.0 mU/ml. The magnitude of the cAMP response to TSH was unaffected by the presence in the incubation medium of 20% (vol/vol) normal human serum. A cAMP response to TSH was still demonstrable in cells that had been maintained for a period of 22 days in monolayer culture, although the response was reduced in comparison with that given by 4-5 day old cultures.