Haeberli A, Engler H, von Grünigen C, Kohler H, Studer H
Acta Endocrinol (Copenh). 1979 Sep;92(1):105-18. doi: 10.1530/acta.0.0920105.
In this paper additional information on low molecular weight, soluble, intrathyroidal iodocompounds with slow metabolic rate is provided. These compounds have previously been localized autoradiographically within the follicular cells. Radioiodide was administered to rats on a normal iodine intake (6--7 microgram/day) for 80 days to approach isotopic equilibration of the intrathyroidal iodine with the dietary radioiodide. When the isotope was omitted from the diet the intrathyroidal radioiodine was released with an apparent half-life of approximately 12 days. When the individual soluble components carrying radioiodine were analyzed after separation on Sephadex G-200, different apparent half-lives were found, the half-life of thyroglobulin (Tgb) being roughly 10 days and that of the low molecular weight iodocomounds being in the order of 60 to 100 days or more. In addition to the soluble low molecular weight iodocompounds, the radioactivity in the particulate fraction increased by 100% during the tracer washout when compared to Tgb and the total soluble fraction. The soluble slow turnover iodocompounds contained a higher percentage of carbohydrate and total iodine than Tgb, while the relative amounts of each sugar analyzed (hexoses, fucose, hexosamine and sialic acid) were close to those in Tgb. Sephadex G-25 chromatography of the low molecular weight iodocompounds obtained after Sephadex G-200 separation resulted in the separation of 4 peaks. Two peaks identified as iodopeptides could be further analyzed. The carbohydrate composition of these peptides was similar to that of 2 glycopeptides obtained after in vitro enzymatic hydrolysis of purified Tgb with pronase. Slow equilibration with radioiodine, long apparent intrathyroidal half-life and carbohydrate content similar to that of Tgb, taken together with previously published data on intracellular localization of soluble intrathyroidal iodocompounds, suggest that the low molecular weight iodocompounds are products of in vivo hydrolysis of engulfed Tgb droplets.
本文提供了关于低分子量、可溶性、甲状腺内代谢率缓慢的碘化合物的更多信息。这些化合物先前已通过放射自显影定位在滤泡细胞内。给正常碘摄入量（6 - 7微克/天）的大鼠注射放射性碘80天，以使甲状腺内碘与饮食中的放射性碘达到同位素平衡。当饮食中不再添加同位素时，甲状腺内的放射性碘以约12天的表观半衰期释放。当在Sephadex G - 200上分离后分析携带放射性碘的各个可溶性组分时，发现了不同的表观半衰期，甲状腺球蛋白（Tgb）的半衰期约为10天，低分子量碘化合物的半衰期约为60至100天或更长。除了可溶性低分子量碘化合物外，与Tgb和总可溶性组分相比，在示踪剂洗脱期间颗粒部分的放射性增加了100%。可溶性周转缓慢的碘化合物比Tgb含有更高百分比的碳水化合物和总碘，而分析的每种糖（己糖、岩藻糖、己糖胺和唾液酸）的相对含量与Tgb中的接近。对Sephadex G - 200分离后得到的低分子量碘化合物进行Sephadex G - 25层析，得到4个峰的分离。两个被鉴定为碘肽的峰可以进一步分析。这些肽的碳水化合物组成与用链霉蛋白酶对纯化的Tgb进行体外酶水解后得到的2种糖肽相似。与放射性碘的缓慢平衡、甲状腺内较长的表观半衰期以及与Tgb相似的碳水化合物含量，再加上先前发表的关于甲状腺内可溶性碘化合物细胞内定位的数据，表明低分子量碘化合物是被吞噬的Tgb液滴体内水解的产物。
