[Dissociation between the effects of TSH and dibutyryl cAMP on thyroxine secretion by isolated thyroid cells. Similarity of actions on iodide uptake and thyroxine synthesis (author's transl)].

We have compared the effects of TSH and dibutyryl-cAMP (DBC) on three parameters of iodine metabolism in isolated hog thyroid cells: iodide uptake, thyroxine (T4) synthesis and T4 secretion. As WILSON, we observed a similarity between TSH (60 mU/ml) and DBC (3 mM) actions on iodide uptake and T4 synthesis. But DBC did not reproduce the TSH stimulation of T4 secretion. Since TSH increased T4 secretion in the presence of DBC, the lack of effect of DBC was not due to an alteration of the secretory process by DBC. The present observation might suggest that the stimulatory effect of TSH on T4 secretion by isolated thyroid cells is not mediated by the adenyl cyclase-cAMP system, or could indicate that DBC may not act like cAMP on some target enzyme systems.