Ether Link Cleavage Is the Major Pathway of Iodothyronine Metabolism in the Phagocytosing Human Leukocyte and also Occurs In Vivo in the Rat

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Abstract

These studies were performed to test the hypothesis that ether link cleavage (ELC) is an important pathway for the metabolism of thyroxine (T4) in the phagocytosing human leukocyte. When tyrosyl ring-labeled [125I]T4([Tyr125I]T4) was incubated with phagocytosing leukocytes, 50% of the degraded label was converted into [125I]3,5-diiodotyrosine ([125I]DIT). Of the remaining [Tyr125I]T4 that was degraded, two-thirds was recovered as [125I]-nonextractable iodine ([125I]NEI), and one-third as [125I]iodide. The production of [125I]DIT was not observed when phenolic ring-labeled [125I]T4 ([Phen125I]T4) was used, although [125I]NEI and [125I]iodide were produced. None of these iodinated compounds were formed in leukocytes that were not carrying out phagocytosis.

Authors

Albert G. Burger, Dennis Engler, Ulrich Buergi, Michael Weissel, Gertraud Steiger, Sidney H. Ingbar, Richard E. Rosin, Bernard M. Babior