Effects of thyrotropin, prostaglandin E1 and iodide on cyclic 3',5'-AMP concentration in dog thyroid slices.

The kinetics and concentration effect on the relationship of thyrotropin (TSH) action on cyclic 3′,5′-AMP concentration has been studied in dog thyroid slices in vitro. TSH markedly increased cyclic 3′,5′-AMP level after 5 min, the effect reached a plateau after 10-60 min and slowly declined afterwards. TSH enhanced in parallel the cyclic 3′,5′-AMP level and the binding of iodide to proteins. For this latter effect of TSH, the four criteria of the validity of the Sutherland model for a hormonal action are therefore fulfilled. The effect of TSH on cyclic 3′,5′-AMP concentration in thyroid did not require the presence of a methylxanthine inhibitor of cyclic 3′,5′-AMP phosphodiesterase in the medium. Prostaglandin E1 increased cyclic 3′,5′-AMP levels in control and stimulated slices. The omission of Ca2+ in the incubation medium decreased the action of TSH but partial replacement of Na+ by K+ had little effect. Iodide, 1 μM to 100 μM, inhibited the action of TSH. This inhibitory effect was relieved by NaClO4, methimazole and propylthiouracil (1 mM). The possible role of this inhibitory effect in an intracellular regulatory mechanism is discussed. © 1973.In VitroJournal ArticleSCOPUS: ar.j