| Literature DB >> 23865 |
B Höffken, R Ködding, A Von Zur Mühlen, T Hehrmann, H Jüppner, R D Hesch.
Abstract
The nature of the conversion of thyroxine (T4) to triiodothyronine (T3) and reverse triiodothyronine (rT3) was investigated in rat liver homogenate and microsomes. A 6-fold rise of T3 and 2.5-fold rise of rT3 levels determined by specific radioimmunoassays was observed over 6 h after the addition of T4. An enzymic process is suggested that converts T4 to T3 and rT3. For T3 the optimal pH is 6 and for rT3, 9.5. The converting activity for both T3 and rT3 is temperature dependent and can be suppressed by heat, H2O2, merthiolate and by 5-propyl-2-thiouracil. rT3 and to a lesser degree iodide, were able to inhibit the production of T3 in a dose related fashion. Therefore the pH dependency, rT3 and iodide may regulate the availability of T3 or rT3 depending on the metabolic requirements of thyroid hormones.Entities:
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Year: 1978 PMID： 23865 DOI： 10.1016/0304-4165(78)90126-5
Source DB: PubMed Journal: Biochim Biophys Acta ISSN： 0006-3002