Uptake of 3,5,3'-L-Triiodothyronine into Bullfrog Red Blood Cells Mediated by Plasma Membrane Binding Sites : Endocrinology

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概要

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• To examine the mechanism of thyroid hormone transport into the bullfrog red blood cells (RBCs), the uptake of 3,5,3'-L-triiodothyronine (T_3) into the intact RBCs of bullfrog and the binding of T_3 to the purified plasma membranes were studied. The specific T_3 uptake into the adult RBCs was saturable at a certain T_3 concentration and temperature-dependent showing maximum binding at 15℃. The uptake of iodothyronines into RBCs showed stereospecificity for T_3 (T_3>>3,5,3'-D-triiodothyronine = L-thyroxine). The nuclear uptake of T_3 was only a few percent of the cellular associated T_3 after incubating at 15℃ for 1hr. Monodansylcadaverine, an inhibitor of receptor-mediated endocytosis, blocked T_3 uptake into the adult RBCs even at 0℃, with a half maximal inhibitory concentration of 65μM. The effect of MDC strongly suggests that even at 0℃ T_3 should enter bullfrog RBCs by receptor-mediated endocytosis. To clarify the presence of the T_3 binding sites on the plasma membranes, we purified the plasma membranes from adult RBCs. Scatchard analysis revealed the presence of two classes of T_3 binding sites on the plasma membrane: a high affinity-low capacity site (Kd_1: 36.0±12.7nM, MBC_1: 14.8±6.7fmol/μg protein), and a low affinity-high capacity site (Kd_2: 5.34±1.54μM, MBC_2: 2.44±0.51pmol/μg). From these results it is suggested that T_3 initially binds to the specific binding sites on the cell surface of the bullfrog RBCs, and then enters the cells by receptor-mediated endocytosis.

• 社団法人日本動物学会の論文
• 1989-08-15

著者

• Horiuchi Ryuya

  Institute Of Endocrinology Gunma University

• Koya Sakuji

  Institute Of Endocrinology Gunma University

• Takikawa Hiroo

  Institute of Endocrinology, Gunma University

• Takikawa Hiroo

  Institute Of Endocrinology Gunma University

• YAMAUCHI KIYOSHI

  Institute of Endocrinology, Gunma University

• Yamauchi Kiyoshi

  Institute Of Endocrinology Gunma University

関連論文

• Seasonal Changes in Gonadotropin Activity of the Pituitary Gland in the Adult Male Japanese Red-bellied Newt, Cynops pyrrhogaster pyrrhogaster
• Involvement of Four Hormones in Thyroxine Deiodination in Several Tissues of Immature Yearling Masu Salmon, Oncorhynchus masou
• Uptake Mechanism of 3, 5, 3'-Triiodothyronine in Masu Salmon Oncorhynchus masou Hepatocytes
• Uptake of 3,5,3'-L-Triiodothyronine into Bullfrog Red Blood Cells Mediated by Plasma Membrane Binding Sites : Endocrinology

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