Identification of Thyroidal Iodoamino Acids by Gel Filtration and Automated127I Determination

Abstract

Hydrolysates of thyroid tissue from 4 patients with diverse thyroid disease have been subjected to gel filtration on Sephadex G-25. Iodide (I"), monoiodotyroslne (MIT), diiodotyrosine (DIT), triiodothyronlne (T3) and thyroxin (T4) were determined both by an automated chemical analysis of I"'' and by ll31 counting. Detection of these compounds by 1*27 analysis reliably reflects their presence in the thyroid gland and under certain circumstances may allow a more accurate evaluation of possible iodotyrosine coupling defects than I131 counting. Aporttonof the thyroid gland from one of the patients was stored for a prolonged period at -4 C. Gel filtration of a hydrolysate of this stored thyroid tissue gave results similar to those obtained immedlatly post thyroldectomy. Gel filtration of thyroid hydrolysates offers a simple, reliable and highly reproducible means of separating iodide and the thyroidal iodoamino acids.