title: Induction of the thyroxine (T4) to triiodothyronine (T3) converting enzyme in rat liver by thyroid hormones and analogs.
abstract: In thyroidectomized, unsubstituted rats the T4 to T3 converting activity of liver homogenate is reduced to about 30% of that in unoperated control animals. The enzyme activity can be reinduced dose-dependently with T4. To achieve a normal activity, high, non-physiological plasma T4 concentrations are needed. Plasma T3 levels are much better correlated to the T4 to T3 converting activity. Pure T3 proved to be a more potent enzyme inducer than T4. No difference could be detected between L- and D-T3. Tyrosine, diiodotyrosine, 3,3'-diiodothyronine and 3,3',5'-T3 (reverse-T3) showed no inductive effect for the enzyme. These results demonstrate that the T4 to T3 converting enzyme is specific and shows regulatory properties.
mesh_terms: D000818:Animals; D004790:Enzyme Induction / Q000187:drug effects; D007453:Iodide Peroxidase / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D008297:Male; D010544:Peroxidases / Q000378:metabolism*; D051381:Rats; D013963:Thyroid Hormones / Q000494:pharmacology*; D013965:Thyroidectomy; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D013963:Thyroid Hormones; D014284:Triiodothyronine; D010544:Peroxidases; D007453:Iodide Peroxidase; D013974:Thyroxine