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Titolo:
DOWN-REGULATION OF TYPE-II L-THYROXINE, 5'-MONODEIODINASE IN CULTUREDGC CELLS - DIFFERENT PATHWAYS OF REGULATION BY L-TRIIODOTHYRONINE AND3,3',5'-TRIIODO-L-THYRONINE
Autore:
HALPERIN Y; SHAPIRO LE; SURKS MI;
Indirizzi:
ALBERT EINSTEIN COLL MED,MONTEFIORE MED CTR,DEPT MED,DIV ENDOCRINOL,111 E 210TH ST BRONX NY 10467 ALBERT EINSTEIN COLL MED,MONTEFIORE MED CTR,DEPT MED,DIV ENDOCRINOL BRONX NY 10467
Titolo Testata:
Endocrinology
fascicolo: 4, volume: 135, anno: 1994,
pagine: 1464 - 1469
SICI:
0013-7227(1994)135:4<1464:DOTL5I>2.0.ZU;2-1
Fonte:
ISI
Lingua:
ENG
Soggetto:
GROWTH-HORMONE PRODUCTION; RAT CEREBRAL-CORTEX; THYROID-HORMONE; IODOTHYRONINE 5'-DEIODINASE; PITUITARY; T3; 3,5,3'-TRIIODOTHYRONINE; RECEPTORS; INVITRO; SERUM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
28
Recensione:
Indirizzi per estratti:
Citazione:
Y. Halperin et al., "DOWN-REGULATION OF TYPE-II L-THYROXINE, 5'-MONODEIODINASE IN CULTUREDGC CELLS - DIFFERENT PATHWAYS OF REGULATION BY L-TRIIODOTHYRONINE AND3,3',5'-TRIIODO-L-THYRONINE", Endocrinology, 135(4), 1994, pp. 1464-1469

Abstract

The current consensus is that iodothyronines down-regulate type II T-4 monodeiodinase (5'-DII) by an extranuclear acceleration of enzyme inactivation. We have investigated 5'-DII regulation in cultured GC cells, in which thyroid hormone responses are mediated by nuclear thyroid receptor (TR). GC cells actively converted T-4 to T-3, independent of propylthiouracil and with a K-m of 1.4 nM, which are characteristics of 5'-DII. When GC cells were incubated with 10 nM T-3, the K-m was notaffected. However, the maximum velocity was significantly down-regulated by 10 nM T-3 from 0.15 to 0.018 pmol/mg protein min. Dose-responsestudies showed that a 50% reduction in enzyme activity was achieved with either 0.25 nM T-3 or 12 nM rT(3). Time-course studies showed thata 50% reduction in enzyme activity occurred after 40 min of incubation with 100 nM rT(3) and after 160 min of incubation with 10 nM T-3. The down-regulation of 5'-DII by physiological concentrations of T-3 hasthe characteristics of an effect that is mediated by nuclear TR. Our studies, therefore, suggest that down-regulation of 5'-DII by these iodothyronines in GC cells may occur by different mechanisms: enzyme inactivation for rT(3), in agreement with the current consensus, and decreased enzyme production for T-3 probably mediated by TR.

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Documento generato il 13/08/20 alle ore 13:33:58