2024-03-29T06:52:01Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/242522020-02-17T12:31:56Zcom_10261_22com_10261_1col_10261_275
http://hdl.handle.net/10261/24252
24491
Transthyretin regulates thyroid hormone levels in the choroid plexus, but not in the brain parenchyma: study in a transthyretin-null mouse model
Endocrine Society
2000
artículo
Almeida Palha, Joana
Fernandes, Rui
Morreale de Escobar, Gabriella
rp13386
Episkopou, Vasso
Gottesman, Max
Saraiva, Maria João
2000-09
6 pages, 3 figures, 2 tables.-- Presented in part in abstract form at the 26th Annual
Meeting of the European Thyroid Association, Milan, Italy, August 28
to September 1, 1999.-- This is part of the Ph.D. thesis of J.A.P., University
of Porto, Porto, Portugal.
Transthyretin (TTR) is the major T4-binding protein in rodents. Using a TTR-null mouse model we asked the following questions. 1) Do other T4 binding moieties replace TTR in the cerebrospinal fluid (CSF)? 2) Are the low whole brain total T4 levels found in this mouse model associated with hypothyroidism, e.g. increased 5'-deiodinase type 2 (D2) activity and RC3-neurogranin messenger RNA levels? 3) Which brain regions account for the decreased total whole brain T4 levels? 4) Are there changes in T3 levels in the brain? Our results show the following. 1) No other T4-binding protein replaces TTR in the CSF of the TTR-null mice. 2) D2 activity is normal in the cortex, cerebellum, and hippocampus, and total brain RC3-neurogranin messenger RNA levels are not altered. 3) T4 levels measured in the cortex, cerebellum, and hippocampus are normal. However T4 and T3 levels in the choroid plexus are only 14% and 48% of the normal values, respectively. 4) T3 levels are normal in the brain parenchyma. The data presented here suggest that TTR influences thyroid hormone levels in the choroid plexus, but not in the brain. Interference with the blood-choroid-plexus-CSF-TTR-mediated route of T4 entry into the brain caused by the absence of TTR does not produce measurable features of hypothyroidism. It thus appears that TTR is not required for T4 entry or for maintenance of the euthyroid state in the mouse brain.
openAccess
Endocrinology
2000
141
3267
3272