The integrity of the ether linkage during thyroxine metabolism in man

Constance S. Pittman; Virginia H. Read; Joseph B. Chambers; Haruyoshi Nakafuji

doi:10.1172/JCI106246

Department of Medicine, University of Alabama Medical Center, Birmingham, Alabama 35233

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Department of Medicine, University of Alabama Medical Center, Birmingham, Alabama 35233

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Department of Medicine, University of Alabama Medical Center, Birmingham, Alabama 35233

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Department of Medicine, University of Alabama Medical Center, Birmingham, Alabama 35233

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Published in Volume 49, Issue 2 on February 1, 1970
J Clin Invest. 1970;49(2):373–380. https://doi.org/10.1172/JCI106246.
© 1970 The American Society for Clinical Investigation

Published February 1, 1970 - Version history

The structures of thyroxine metabolites after total deiodination bear on the mode of thyroxine (T₄) action in vivo. The present study was undertaken to determine the integrity of the ether linkage during thyroxine metabolism in man. Normal volunteers were given simultaneous intravenous injections of two thyroxines labeled with either ¹⁴C or ³H on the opposite sides of the ether linkage, D,L-[α,β-³H]T₄ and D,L-[phenolic ring-¹⁴C]T₄. The ratio of alanine side chain to phenolic ring which was measured as ³H:¹⁴C ratio was found to remain constant in the serum, urine, and feces during the subsequent 3 wk. The disappearance rates of the ³H and ¹⁴C radioactivity from blood were similar. The values of half-life were in the ranges of 4.2-6.7 days. 51-63% of the ³H and 50-57% of the ¹⁴C doses were recovered from urine and 13-20% of the ³H and 15-20% of the ¹⁴C doses were recovered from feces. Chromatography of the urinary metabolites confirmed that the phenolic ring and the nonphenolic ring including at least part of the side chain remained linked together.