Metabolism of sulfoconjugated thyroid hormone derivatives in developing sheep
| Autor: | D. A. Fisher, A. L. Reviczky, Wen-Sheng Huang, D. H. Polk, Sing-Yung Wu |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Aging
medicine.medical_specialty Triiodothyronine Reverse Physiology Endocrinology Diabetes and Metabolism Biology Embryonic and Fetal Development chemistry.chemical_compound Sulfation Physiology (medical) Internal medicine medicine Animals Fetus Sheep Triiodothyronine Thyroid Metabolism Fetal Blood Reverse triiodothyronine Thyroxine medicine.anatomical_structure Endocrinology Animals Newborn chemistry Clearance rate Hormone |
| Zdroj: | American Journal of Physiology-Endocrinology and Metabolism. 266:E892-E896 |
| ISSN: | 1522-1555 0193-1849 |
| DOI: | 10.1152/ajpendo.1994.266.6.e892 |
| Popis: | Although the production of thyroxine (T4) in the developing ovine fetus ranges from 20 to 50 micrograms.kg-1.day-1, production rates for 3,5,3'-triiodothyronine (T3) average only 1-2 micrograms.kg-1.day-1, whereas reverse T3 (rT3) production rates approach 5-6 micrograms.kg-1.day-1. Thus the fate of the majority of fetal T4 production is uncertain. Recently we have reported significant concentrations of various thyroid hormone sulfoconjugates in serum and other fetal compartments. In the present study, we used steady-state kinetic techniques in developing sheep to establish the clearance and production rates for T4, T3, and rT3 sulfates. These studies confirm that T4, T3, and rT3 sulfate are predominant metabolites of thyroid hormone in the developing ovine fetus. Plasma clearance rates for T3, T4, and rT3 sulfates are low in the fetus, averaging 0.67 +/- 0.07, 1.46 +/- 0.11, and 4.1 +/- 1 ml.kg-1.min-1, respectively. Clearance rates for these thyrosulfoconjugates increase two to fourfold postnatally, probably reflecting increased activity of 5'-monodeiodinase after birth. Moreover, fetal production rates for these sulfated thyroid hormone metabolites exceed those of 2-wk-old sheep 4- to 10-fold. The data suggest that a significant route of fetal T4 metabolism is sulfation followed by deiodination to rT3 sulfate. |
| Databáze: | OpenAIRE |
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