Effects of thyrotropin, sodium fluoride and ions on thyroid slice metabolism

Abstract

Activation of adenyl cyclase with resultant formation of cyclic 3′, 5′-AMP has been implicated in the action of thyrotropin (TSH) on thyroid. Since sodium fluoride increases adenyl cyclase activity in thyroid and also stimulates thyroid slice glucose oxidation and phospholipogenesis, we compared the effects of TSH and fluoride, singly and in combination, on glucose-1- 14C oxidation and 32P incorporation into phospholipid in sheep thyroid slices. Although these effects were superficially alike, and were similarly affected by changes in the ionic composition of the incubation medium, no synergism between TSH and fluoride effects was noted and stimulation induced by maximal effective concentrations of NaF was augmented by the addition of TSH. These data suggest that the sites at which these compounds interact on the thyroid to exert their effects are different. The significance of these findings in relation to the possible role of the adenyl cyclase-cyclic 3′, 5′-AMP system in controlling thyroid metabolism is discussed.