Portman O W, Alexander M
Atherosclerosis. 1985 Sep;56(3):283-99. doi: 10.1016/0021-9150(85)90004-8.
Low density lipoproteins labeled with [125I]tyramine cellobiose ([125I]TC-LDL) were removed from the circulation of squirrel monkeys at a similar but slightly slower rate than LDLs labeled with 125I, [125I]hydroxyphenyl propionic acid, or [3H]leucine. After the simultaneous injection of [125I]TC-LDL and [131I]LDL labeled with 131ICl, the 125I was also removed at a slightly slower rate than 131I. Most of the radioactivity was retained in tissues and not excreted during the 24 h after injection of [125I]TC-LDL. This finding supports the claim of Pittman et al. [18] that [125I]TC-LDL can be used to determine the irreversible uptake of LDL by different tissues. The liver cleared more LDL than any other organ, but the adrenals and ovaries were more active per gram. Trichloroacetic acid (TCA) precipitated more than 80% of the radioactivity in the tissues that had low 125I uptake, but only about 50% of the 125I in more active tissues (liver, adrenals, ovaries, and spleen). Only a small percentage of 125I in urine and bile was TCA-precipitable. In the dual label experiment with [125I]TC-LDL and [131I]LDL there was a selective retention of 125I in samples from liver, spleen, adrenals, and, perhaps testes, and an almost complete selectivity for 125I in bile and feces. The aortic intima plus inner media (AIM) cleared much less LDL than other tissues, but the uptake by the entire AIM was proportional to the cholesterol concentration and weight of the total AIM. There was, however, no correlation between either of the latter two measurements and the uptake of LDL per gram of AIM. The concentration of LDL apolipoprotein in the AIM determined by immunoelectrophoresis did not correlate significantly with LDL uptake per gram. Both the amounts of LDL apolipoprotein present and labeled LDL taken up by the AIM depended on the weight of the sample, and perhaps on the weight of intima in the sample.
用[125I]纤维二糖酪胺（[125I]TC-LDL）标记的低密度脂蛋白从松鼠猴循环中清除的速率与用125I、[125I]羟苯基丙酸或[3H]亮氨酸标记的低密度脂蛋白相似，但略慢。同时注射[125I]TC-LDL和用131ICl标记的[131I]LDL后，125I的清除速率也比131I略慢。注射[125I]TC-LDL后的24小时内，大部分放射性保留在组织中，未被排泄。这一发现支持了皮特曼等人[18]的观点，即[125I]TC-LDL可用于确定不同组织对低密度脂蛋白的不可逆摄取。肝脏清除的低密度脂蛋白比其他任何器官都多，但每克肾上腺和卵巢的活性更高。三氯乙酸（TCA）沉淀了125I摄取量低的组织中80%以上的放射性，但在活性较高的组织（肝脏、肾上腺、卵巢和脾脏）中仅沉淀了约50%的125I。尿液和胆汁中只有一小部分125I可被TCA沉淀。在[125I]TC-LDL和[131I]LDL的双标记实验中，肝脏、脾脏、肾上腺以及可能还有睾丸的样本中存在125I的选择性保留，并且在胆汁和粪便中对125I几乎具有完全选择性。主动脉内膜加内中膜（AIM）清除的低密度脂蛋白比其他组织少得多，但整个AIM的摄取量与胆固醇浓度和总AIM的重量成正比。然而，后两项测量中的任何一项与每克AIM摄取的低密度脂蛋白之间均无相关性。通过免疫电泳测定的AIM中低密度脂蛋白载脂蛋白的浓度与每克低密度脂蛋白摄取量无显著相关性。AIM中存在的低密度脂蛋白载脂蛋白的量以及摄取的标记低密度脂蛋白的量均取决于样本的重量，可能还取决于样本中内膜的重量。
