METABOLITES OF RADIOACTIVE L-THYROXINE AND L-TRIIODOTHYRONINE1

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Abstract
The major metabolites of thyroxine and triiodothyronine which occur in blood and urine were studied by 3 techniques, namely, column chromatography, two-dimensional chromatography and paper electro-phoresis. These metabolites are found in much larger amounts in the urine of the dehepatized dog than in the urine of the normal dog and in large amounts in the plasma, particularly, in the dehepatized, nephrectomized dog. The major metabolites of thyroxine include the glucuroconjugate of thyroxine and 2 unidentified iodine compounds, one of which was also present in the conjugated form. Triiodothyronine was rarely seen on paper chromatograms and then only in small amounts. Small amounts of tetraiodothyroacetic acid, which is not separated from thyroxine by column chromatography, were found on paper chromatograms of serum. The major metabolites of triiodothyronine included 2 unidentified compounds and a smaller amount of conjugated triiodothyronine. Radioactivity was found in the region of triiodothyroacetic acid in paper electrophoretic patterns but not in that region on paper chromatograms of urine or serum.