Lee J, Coleman R E, Sherman L A
J Lab Clin Med. 1977 Apr;89(4):836-44.
Aggregate formation on gel chromatography and shortened in vivo t1/2 have been shown to result from the usual chloramine-T (CT) radioiodination of proteins. A modified CT method with decreased CT: protein ratio has ben advocated, particularly for use in the 125I-fibrinogen uptake test. In the present study, such modified CT procedures with 131I were assessed by simultaneous injection in rabbits of iodine-125 monochloride protein standards along with the 131I-CT proteins. Standard clearance analyses were performed. For both albumin and fibrinogen a much reduced CT:protein ratio was required before satisfactory in vivo proteins were obtained. The ratio differed for the two proteins, with fibrinogen being more susceptible to CT-induced aggregate formation. Intermediate CT:protein ratios resulted in denaturation of only a portion of the labeled proteins as manifested by a low C1 with a normal t1/2 for the slow component. At intermediate ratios, unaggregated protein displayed abnormal clearance kinetics, indicating that denaturation was not solely the result of aggregates. The results indicated modified CT radioiodination can be used for in vivo studies, but only if carefully compared in vivo with more generally used radiolabeling procedures.
凝胶色谱上的聚集体形成以及体内半衰期缩短已被证明是蛋白质常规氯胺 - T（CT）放射性碘化的结果。有人提倡使用一种CT与蛋白质比例降低的改良CT方法，特别是用于¹²⁵I - 纤维蛋白原摄取试验。在本研究中，通过将一氯化碘 - ¹²⁵蛋白质标准品与¹³¹I - CT蛋白质同时注射到兔子体内，对这种用¹³¹I的改良CT程序进行了评估。进行了标准清除分析。对于白蛋白和纤维蛋白原，在获得令人满意的体内蛋白质之前，都需要大大降低CT与蛋白质的比例。这两种蛋白质的比例不同，纤维蛋白原更容易受到CT诱导的聚集体形成的影响。中间的CT与蛋白质比例导致只有一部分标记蛋白质变性，表现为低C1且慢成分的半衰期正常。在中间比例下，未聚集的蛋白质显示出异常的清除动力学，表明变性不仅仅是聚集体的结果。结果表明，改良的CT放射性碘化可用于体内研究，但前提是必须在体内与更常用的放射性标记程序进行仔细比较。
