THYROID HORMONES-CELL INTERACTIONS

据报道，甲状腺激素进入细胞是通过 被动扩散、易化扩散和受体介导扩散 内吞作用 我们正在几种组织中研究这一过程： 大鼠骨骼肌，连续培养的大鼠肌细胞和人 肝癌细胞 使用HepG2人肝癌细胞，我们已经表明， 大约50%的T3摄取是饱和的，并且这种饱和摄取是 强烈抑制根皮素，抑制剂苯妥英钠，葡萄糖和 非电解质转运。 抑制T3和T4摄取的机制 可能是由于根皮素的双酚结构，使其作为一种 竞争性拮抗剂，或间接通过其抑制葡萄糖 运输 在无葡萄糖培养基中孵育细胞也抑制T3 吸收，但不像根皮素那样完全。 大鼠成肌细胞（L6）也被证明具有饱和吸收 甲状腺激素和工作正在进行中，以确定其特征 在未分化和分化的细胞中。 在完整的 骨骼肌，T3摄取已被证明增加的影响下， 胰岛素。 这种增加被哇巴因阻止，哇巴因是钠钾的抑制剂 ATP酶，以及在无Na培养基中孵育。

The entry of thyroid hormones into cells has been reported to occur via passive diffusion, facilitated diffusion and receptor-mediated endocytosis. We are studying this process in several tissues: intact skeletal muscle of the rat, continuously cultured rat myocytes and human hepatoma cells. Using the HepG2 human hepatoma cells, we have shown that about 50% of T3 uptake is saturable, and that this saturable uptake is strongly inhibited by phloretin, an inhibitor of dilantin, glucose and non-electrolyte transport. The mechanism of inhibition of T3 and T4 uptake could be due to the biphenol structure of phloretin, causing it to act as a competitive antagonist, or indirectly through its inhibition of glucose transport. Incubation of cells in glucose-free medium also inhibits T3 uptake, but not as completely as phloretin. The rat myoblasts (L6) have also been shown to possess a saturable uptake system from thyroid hormone and work is underway to characterize this process in undifferentiated and differentiated cells. In the intact skeletal muscle, T3 uptake has been shown to increase under the influence of insulin. This increase is prevented by ouabain, an inhibitor of Na-K ATPase, as well as by incubation in a Na-free medium.