Evaluation of the rat thyroid cell strain FRTL-5 as an in-vitro bioassay system for thyrotrophin.
The cyclic AMP response to bovine TSH was characterized in a strain of rat thyroid follicular cells ( FRTL -5) maintained in continuous culture. Significant stimulation of intracellular cyclic AMP was attained at a TSH dose of 5 muu./ml. Cyclic AMP accumulation continued to increase, at higher TSH doses, with no evidence for attainment of a maximum level at the highest dose tested (5 mu./ml). The precision of TSH measurement was better than 10% over the range 50-5000 muu./ml, comparing favourably with that observed with analogous assays based on human cells, tissue slices or membrane preparations. Using sequential subcultures of FRTL -5 cells, the between-assay variation in response to a single dose of a standard preparation of bovine TSH (53/11; 370 muu./ml) was of the order of 20% which compared favourably with the between-assay variation observed with different cultures of human thyroid cells. Prolongation of the incubation of FRTL -5 cells with TSH to 3 h revealed a progressive increase in the extracellular accumulation of cyclic AMP. Addition of TSH to resting FRTL -5 cells resulted in a stimulation of inorganic iodide uptake with pronounced bell-shaped dose-response characteristics. Thus a maximum uptake was observed at a TSH dose of 100 muu./ml with a significant reduction at higher doses. Acute stimulation of cells with TSH (100 muu./ml) resulted in a rapid and marked alteration in cell morphology, with evidence of cellular retraction and surface ruffling.
D000818:Animals; D001681:Biological Assay / Q000379:methods*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D007455:Iodine / Q000378:metabolism; D051381:Rats; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013972:Thyrotropin / Q000032:analysis* / Q000494:pharmacology
D013972:Thyrotropin; D007455:Iodine; D000242:Cyclic AMP