Biosynthesis and metabolism of 2-iodohexadecanal in cultured dog thyroid cells.
2-Iodohexadecanal (2-IHDA) is a major thyroid iodolipid. It mimics the main regulatory effects of iodide on thyroid metabolism: inhibition of H2O2 production and of adenylyl cyclase. The biosynthesis of 2-IHDA and its metabolism have been investigated in cultured dog thyroid cells maintained in a differentiated state by forskolin. Incubation of these cells with [9,10-3H]hexadecan-1-ol or [9,10-3H]palmitic acid labeled several phospholipids, but [9, 10-3H]hexadecan-1-ol was selectively incorporated into plasmenylethanolamine. In the presence of an exogenous H2O2 generating system (glucose oxidase), iodide induced the production of [9,10-3H]2-IHDA from [9,10-3H]hexadecan-1-ol-labeled cells but not from [9,10-3H]palmitic acid-labeled cells. 2-IHDA was also generated during the lactoperoxidase-catalyzed iodination of brain and heart plasmalogens, and of ethyl hexadec-1-enyl ether, a synthetic vinyl ether-containing compound. Taken together, these results show that thyroid 2-IHDA is derived from plasmenylethanolamine via an attack of reactive iodine on the vinyl ether group. 2-Iodohexadecan-1-ol (2-IHDO) was also detected in these studies; it was formed later than 2-IHDA, and thyroid cells converted exogenous 2-IHDA into 2-IHDO in a time-dependent way. The ratio of 2-IHDO/2-IHDA increased with H2O2 production and decreased as a function of iodide concentration. An aldehyde-reducing activity was detected in subcellular fractions of the horse thyroid. No formation of 2-iodohexadecanoic acid could be detected. Reduction into the biologically inactive 2-IHDO is thus a major metabolic pathway of 2-IHDA in dog thyrocytes.
Panneels
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V
Institute of Interdisciplinary Research, School of Medicine, Free University of Brussels, Belgium.
Macours
P
P
Van den Bergen
H
H
Braekman
J C
JC
Van Sande
J
J
Boeynaems
J M
JM
D000449:Aldehyde Reductase / Q000032:analysis; D000447:Aldehydes / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004285:Dogs; D005233:Fatty Alcohols / Q000378:metabolism; D006736:Horses; D007455:Iodine / Q000378:metabolism*; D010955:Plasmalogens / Q000378:metabolism*; D013961:Thyroid Gland / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D014316:Tritium
D000447:Aldehydes; D005233:Fatty Alcohols; D010955:Plasmalogens; C020791:phosphatidal ethanolamines; D014316:Tritium; C065952:2-iodohexadecanal; C101756:2-iodohexadecan-1-ol; C005031:cetyl alcohol; D007455:Iodine; D000449:Aldehyde Reductase