Uptake of biogenic amines by thyroid glands.

The biogenic amines, serotonin (5-HT) and norepinephrine, activate follicular cells and are endogenous thyroid constitutents. Both amines are taken up by throid lobes incubated in vitro. Uptake of 5-HT is temperature and concentration dependent, is inhibited by chlorimipramine more than by desmethylimipramine, and although it is inhibited by norepinephrine, 5-HT uptake is unaffected by chemical sympathetomy with 6-hydroxydopamine. Electron microscopic radioautography reveals that follicular cells are responsible for uptake of 5-HT and adrenergic nerves for uptake of norepinephrine. These data are consistent with the hypothesis that biogenic amines are intrathyroidal transmitters acting on follicular cells, and that uptake mechanisms may contribute to their inactivation.