This Article Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints, Permissions and Rights Citing Articles Citing Articles via Google Scholar Google Scholar Articles by ANNE GALTON, V. Articles by INGBAR, S. H. Search for Related Content PubMed PubMed Citation Articles by ANNE GALTON, V. Articles by INGBAR, S. H.

Role of Peroxidase and Catalase in the Physiological Deiodination of Thyroxine¹

Department of Physiology, Dartmouth Medical School Hanover, New Hampshire
The Thorndike Memorial Laboratory, Second and Fourth (Harvard) Medical Services, Boston City Hospital, and the Department of Medicine, Harvard Medical School Boston, Massachusetts

This investigation was supported in part by Research Grant A-5892 from the National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland, and in part by the American Cancer Society, Inc., under Grant P-288.

Abstract

Studies in several tissues from the rat and in tissue-free media have afforded evidence that physiological deiodination of thyroxine (T4) and 3,5,3'-triiodothyronine (T3) is mediated by a tissue peroxidase and inhibited by catalase. First, H₂O₂ alone was found capable of deiodinating T4, both in tissue preparations and in tissue-free media. Second, H₂O₂ overcame the absolute requirement of tissue systems for oxygen in deiodinating T4. Third, catalase inhibited, often completely, the deiodination of T4 which occurred in otherwise unsupplemented homogenates of all tissues studied. Fourth, a source of H₂O₂ (glucose-glucose oxidase) was found, which, in appropriate concentrations, stimulated deiodination of both T4 and T3 in unboiled, but not in boiled, homogenates of some tissues and which had no effect in tissue-free media. Furthermore, catalase inhibited the increased deiodination of T4 induced by glucose- glucose oxidase. In addition, the glucose oxidase system also potentiated deiodination of T4 in more organized systems, such as slices of liver and skeletal muscle.

TPN, DPN, ATP and ADP also stimulated deiodination of T4, and their effects were inhibited by catalase, as were the stimulatory effects of hemoglobin and Fe⁺⁺. Evidence is presented which suggests that hemoglobin may enhance deiodination by functioning as a peroxidase and that, in the presence of oxygen, Fe⁺⁺ may lead to H₂O₂ formation.

Footnotes

¹ Presented in part at the 1962 meeting of The Endocrine Society, Chicago, Illinois.

² This work was performed during the tenure of a Life Insurance Medical Research Fellowship.

³ Investigator, Howard Hughes Medical Institute.

Received May 16, 1963.