Molecular structure and biochemical activity of 3,5,3'-triiodothyronamine.

The thyroid hormone decarboxylation product, 3,5,3'-triiodothyronamine (T3AM), has been shown to inhibit the cAMP production stimulated by isoproterenol in turkey erythrocytes. This adrenergic receptor binding inhibition was not shown by the thyroid hormones nor by tyramine, but was observed for 3,5-diiodotyramine, 3,5-diiodothyronamine, and thyronamine. T3AM also inhibits prolactin secretion in cultured pituitary cells as well as domperidon binding in rat corpora striata membranes. T3AM has no thyromimetic activity at the nuclear level. The molecular structure of T3AM, determined as a borosalicylate salt by X-ray diffraction techniques, is the first report of a decarboxylated thyroid hormone analogue.