Transport of thyroxine bound to human prealbumin into rat liver.
Transport of thyroxine bound to human prealbumin into rat liver.
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将与人前白蛋白结合的甲状腺素转运到大鼠肝脏中。
DOI：
10.1152/ajpgi.1985.248.5.g545
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Fierer,G
中科院分区：
文献类型：
--
作者：
Pardridge,WM;Premachandra,BN;Fierer,G
用甲状腺激素结合球蛋白(TBG)缺乏症患者血清和纯化的人前白蛋白研究了甲状腺激素(T4)与人前白蛋白结合的T4在大鼠肝脏的转运。在氯胺酮麻醉大鼠门静脉快速注射混合人血清的同位素后，测定肝脏对~(125)I-T4的单向提取。血清总T4转运到肝脏的百分比为47.6+/-5.2%，与正常血清相比，肝脏T4转运增加了50%。由于T4与白蛋白结合，T4与前白蛋白结合，提示T4与人前白蛋白结合进入大鼠肝脏。门静脉注射生理浓度的人前白蛋白(0.1-0.3 mg/ml)证实了这一点。在此浓度下，与人前白蛋白结合的T4很容易被转运到肝脏。这些研究表明，肝脏微循环中存在的因素抑制了T4与人前白蛋白的结合，使T4与人前白蛋白结合在肝脏中具有很高的转运能力；相反，与大鼠前白蛋白结合的T4在大鼠肝脏中不能转运。人前白蛋白不能隔离血浆中的T4，这可能是TBG在人类中具有选择性优势的基础，它确实隔离了血浆中的T4。
The transport into rat liver of thyroxine (T4) bound to human prealbumin was studied with the use of sera obtained from patients with thyroid hormone-binding globulin (TBG) deficiency and with purified human prealbumin. The unidirectional extraction of 125I-T4 by liver was measured after rapid injection of isotope mixed in human serum into the portal vein of ketamine-anesthetized rats. The percentage of total serum T4 transported into liver was 47.6 +/- 5.2% in subjects with TBG deficiency, and this represented a 50% increase in hepatic T4 transport relative to control human serum. Since T4 is bound to albumin and to prealbumin in complete TBG deficiency, these results suggested that T4 bound to human prealbumin was transported into rat liver. This was confirmed using portal vein injections of human prealbumin at physiological concentrations (0.1-0.3 mg/ml). At these concentrations, T4 bound to human prealbumin was readily transported into liver. These studies suggest factors present in the liver microcirculation inhibit the binding of T4 to human prealbumin such that T4 bound to human prealbumin is highly transportable in liver; conversely, T4 bound to rat prealbumin is not transportable in rat liver. The inability of human prealbumin to sequester T4 in plasma may provide the basis for the selective advantage in humans of TBG, which does sequester T4 in plasma.