Bastiani P, Simon C
Endocrinology. 1982 May;110(5):1716-9. doi: 10.1210/endo-110-5-1716.
To estimate the relative participation of transported and intrathyroidally generated iodide (internal iodide) in the iodination of newly synthesized and preexisting thyroglobulin (Tg) in the rat thyroid, the specific radioactivities (SRAs) of thyroid iodide, Tg, lysosomal iodine, and plasma hormones were followed for 92 h after radioactive iodide injection in intact or hypophysectomized rats. In control rats, the SRA of Tg and lysosomal iodine reached a maximum at 12 h. However, the SRA of lysosomal iodide was always smaller than that of Tg. In contrast, the SRA of hormonal iodide attained a maximum at 48 h. Thus, newly labeled iodine is endocytosed and mixed inside the lysosomes with older previously iodinated molecules; hormone secretion is mainly due to old labeled iodine (i.e. iodine with a high SRA from 48-96 h). These results are consistent with the presence of least two Tg compartments, with different turnover rates and hormone contents. On the other hand, in hypophysectomized rats, the SRA of Tg, lysosomes, and hormones showed only one maximum, at 24 h. Furthermore, the SRAs of Tg and lysosomes were similar at each time interval. It is inferred that in such rats, the old labeled iodine compartment is strongly reduced, and that inside the lysosomes, newly labeled iodine is predominant. Since in hypophysectomized rats, the recycling of iodide is abolished, it is concluded that in normal rats: 1) transported iodide is organified mainly by direct iodination of newly synthesized Tg, independently of TSH, and 2) internal iodide is organified mainly by delayed iodination of preexisting Tg, this process being TSH dependent.
为了评估转运碘和甲状腺内生成的碘（内源性碘）在大鼠甲状腺中新合成的和预先存在的甲状腺球蛋白（Tg）碘化过程中的相对参与度，在完整或垂体切除的大鼠中注射放射性碘后，对甲状腺碘、Tg、溶酶体碘和血浆激素的比放射性（SRA）进行了92小时的跟踪监测。在对照大鼠中，Tg和溶酶体碘的SRA在12小时达到最大值。然而，溶酶体碘的SRA总是小于Tg的SRA。相比之下，激素碘的SRA在48小时达到最大值。因此，新标记的碘被内吞，并在溶酶体内与先前碘化的较老分子混合；激素分泌主要归因于旧的标记碘（即48 - 96小时具有高SRA的碘）。这些结果与至少两个具有不同周转率和激素含量的Tg区室的存在一致。另一方面，在垂体切除的大鼠中，Tg、溶酶体和激素的SRA仅在24小时出现一个最大值。此外，在每个时间间隔，Tg和溶酶体的SRA相似。据推测，在这类大鼠中，旧的标记碘区室大大减少，并且在溶酶体内，新标记的碘占主导。由于在垂体切除的大鼠中，碘的再循环被消除，得出结论：在正常大鼠中，1）转运碘主要通过新合成的Tg的直接碘化而有机化，独立于促甲状腺激素（TSH），并且2）内源性碘主要通过预先存在的Tg的延迟碘化而有机化，这个过程依赖于TSH。
