Contribution fron local conversion of thyroxine to 3,5,3'-triiodothyronine to intracellular 3,5,3'-triiodothyronine in several organs in hypothyroid rats at isotope equilibrium
van Doorn, J.; Roelfsema, F.; van der Heide, D.
Acta Endocrinologica 101(3): 386-396
1982
ISSN/ISBN: 0001-5598 PMID: 7148336 Document Number: 188848
The intracellular conversion of T4 T4 was present in all tissues investigated. There was substantially more, although in varying quantities, in the cerebral cortex (79 .+-. 2%), the cerebellum (68 .+-. 4%) and the pituitary gland (53 .+-. 1%) than in the liver (10 .+-. 6%), the kidney (11 .+-. 5%) and thigh muscle (17 .+-. 6%); in the latter tissues most of the 125I-labeled T3 is derived directly from plasma. In the brain of severely hypothyroid rats there is pronounced conversion of T4 to T3 and effective binding of the T3 produced while the T3 in the liver, kidney, and muscle is predominantly derived from plasma. At the intracellular level, within the investigated tissues, the locally formed T3 was distributed equally over the subcellular fractions.