Spontaneous deiodination of I-131-labeled thyroxine and related iodophenols on filter paper.

Abstract

I131-thyroxine and other labeled iodophenols in dilute aqueous buffer solution were applied to filter paper strips for chromatography, and the applied samples were permitted to dry for periods ranging from 0–240 min before the strips were suspended in the chromatography jars. Drying for periods as brief as 10–20 min resulted in a spontaneous loss of I131 from the iodinated compounds and an increase in I131-iodide. The extent of the deiodination was quite variable, but, in most experiments with I131-thyroxine, increases in radioiodide from 3- to 5-fold were observed after 15–30 min of drying. Other I131-iodophenols that were tested (3′,3,5-triiodothyronine, 3′,5′,3-triiodothyronine, 3,3′- diiodothyronine, 3,5-diiodotyrosine, 3-monoiodotyrosine) usually displayed radioiodide increases of 100–300% after 20–30 min of drying. These drying times are not unusual for the preparation of filter paper chromatograms, and lack of awareness of the phenomena described in this report could lead to serious error in biolog...