Zone Electrophoresis in Filter Paper of Serum I 131 After Radioiodide Administration. ∗

Abstract

Summary and conclusions

1. Serum from 6 patients who had received radioiodide or I¹³¹-labeled thyroxine was studied by zone electrophoresis in filter paper, at pH 8.6. Most of the I¹³¹ had a mobility intermediate between the alpha₁- and alph₂-glabulins, and a small proportion had the mobility of albumin. No differences were detected between thyroxine added to serum (in vivo) and the thyroid hormone secreted by a normal thyroid gland, by a Graves' disease thyroid gland, and by a functioning thyroid carcinoma. 2. Two patients had received very large doses of radio-iodide and their serum contained large amounts of butanol-insoluble I¹³¹, whereas in the other patients the serum I¹³¹ was largely butanol soluble, and behaved like thyroxine on paper chromatography. These two forms of serum I¹³¹ had similar mobility on zone electrophoresis, but could be differentiated by fractional precipitation of the serum proteins with phosphate buffer. The radioiodine, therefore, was probably attached, in each instance, to a different protein, and the identity in their mobilities was fortuitous. 3. Zone electrophoresis of purified hog thyroglobulin, and of I¹³¹-labeled rat thyroglobulin in a crude thyroid extract, revealed that these substances also had a mobility in the range of the alpha globulins of human serum. This finding is compatible with the previous suggestion that the butanol-insoluble I¹³¹ (“non-thyroxine I¹³¹”) may be thyroglobulin, released into the circulation from damaged thyroid tissue.