Abstract
Triiodothyronine sulfate (T3S) is rapidly deiodinated by the propylthiouracil (PTU)-sensitive type I deiodinase. Here we examined the effects of PTU on plasma T3S levels in rats after intravenous administration of radiolabeled T3 or T3S. Sephadex LH-20 chromatography and high-performance liquid chromatography were used to quantify conjugated and nonconjugated iodothyronines, and iodide was measured as the TCA-soluble radioactivity. In control rats, radioiodide was the main metabolite of both T3 and T3S. Plasma T3S was cleared more rapidly than plasma T3 despite increased binding to plasma proteins. PTU reduced plasma iodide levels by 66 and 78% after T3 and T3S, respectively, and decreased plasma clearance of T3S by 81%. However, PTU had no effect on plasma T3 clearance but increased plasma T3S from injected T3 4.2 times. Biliary excretion of injected T3S was less than 20% in normal rats, in contrast to 70% within 4 h in PTU-treated rats. In conclusion, T3S is an important intermediate in the in vivo metabolism of T3 in rats and accumulates in plasma if type I deiodination is inhibited.
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Selected References
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- Engler D., Burger A. G. The deiodination of the iodothyronines and of their derivatives in man. Endocr Rev. 1984 Spring;5(2):151–184. doi: 10.1210/edrv-5-2-151. [DOI] [PubMed] [Google Scholar]
- FLOCK E. V., BOLLMAN J. L., GRINDLAY J. H. 3,3' Diiodothyronine, a metabolite of 3,5,3' triiodothyronine. Proc Staff Meet Mayo Clin. 1960 Feb 17;35:75–81. [PubMed] [Google Scholar]
- FLOCK E. V., BOLLMAN J. L., GRINDLAY J. H. Conjugates of triodothyronine and its metabolites. Endocrinology. 1960 Sep;67:419–429. doi: 10.1210/endo-67-3-419. [DOI] [PubMed] [Google Scholar]
- FLOCK E. V., BOLLMAN J. L. The effect of thiouracil on the metabolism of L-thyroxine. Biochem J. 1962 Sep;84:621–626. doi: 10.1042/bj0840621. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Flock E. V., Bollman J. L., Owen C. A., Jr, Zollman P. E. Conjugation of thyroid hormones and analogs by the Gunn rat. Endocrinology. 1965 Aug;77(2):303–314. doi: 10.1210/endo-77-2-303. [DOI] [PubMed] [Google Scholar]
- Mol J. A., Visser T. J. Synthesis and some properties of sulfate esters and sulfamates of iodothyronines. Endocrinology. 1985 Jul;117(1):1–7. doi: 10.1210/endo-117-1-1. [DOI] [PubMed] [Google Scholar]
- Otten M. H., Mol J. A., Visser T. J. Sulfation preceding deiodination of iodothyronines in rat hepatocytes. Science. 1983 Jul 1;221(4605):81–83. doi: 10.1126/science.6857270. [DOI] [PubMed] [Google Scholar]
- ROCHE J., MICHEL R., CLOSON J., MICHEL O. Sur la sulfoconjugaison hépatique de la 3, 5, 3'-triiodo-L-thyronine et la présence d'un ester sulfurique de cette hormone dans la bile et la plasma. Biochim Biophys Acta. 1959 Jun;33(2):461–469. doi: 10.1016/0006-3002(59)90136-2. [DOI] [PubMed] [Google Scholar]
- ROCHE J., MICHEL R., CLOSON J., MICHEL O. [On the metabolism of the sulfoconjugate of 3,5,3'-triiodothyronine in the rat]. Biochim Biophys Acta. 1960 Feb 26;38:325–332. doi: 10.1016/0006-3002(60)91248-8. [DOI] [PubMed] [Google Scholar]
- Silva J. E., Gordon M. B., Crantz F. R., Leonard J. L., Larsen P. R. Qualitative and quantitative differences in the pathways of extrathyroidal triiodothyronine generation between euthyroid and hypothyroid rats. J Clin Invest. 1984 Apr;73(4):898–907. doi: 10.1172/JCI111313. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Visser T. J., Mol J. A., Otten M. H. Rapid deiodination of triiodothyronine sulfate by rat liver microsomal fraction. Endocrinology. 1983 Apr;112(4):1547–1549. doi: 10.1210/endo-112-4-1547. [DOI] [PubMed] [Google Scholar]