title: Expression profile and thyroid hormone responsiveness of transporters and deiodinases in early embryonic chicken brain development.
abstract: We used the chick embryo to study the mechanisms regulating intracellular TH availability in developing brain. TH-transporters OATP1C1 and MCT8, and deiodinases D1, D2, and D3 were expressed in a region-specific way, well before the onset of endogenous TH secretion. Between day 4 and 10 of development MCT8 and D2 mRNA levels increased, while OATP1C1 and D3 mRNA levels decreased. D2 and D3 mRNAs were translated into active protein, while no D1 activity was detectable. Injection of THs into the yolk 24h before sampling increased TH levels in the brain and resulted in decreased OATP1C1 and increased MCT8 expression in 4-day-old embryos. A compensatory response in deiodinase activity was only observed at day 8. We conclude that THs are active in the early embryonic brain and TH-transporters and deiodinases can regulate their availability. However, the absence of clear compensatory mechanisms at day 4 makes the brain more vulnerable for changes in maternal TH supply.
authors: Laboratory of Comparative Endocrinology, Animal Physiology and Neurobiology Section, Department of Biology, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium.
authors: Stijn L J
authors: SL
authors: Van Herck
authors: Stijn
authors: S
authors: Geysens
authors: Joke
authors: J
authors: Delbaere
authors: Przemko
authors: P
authors: Tylzanowski
authors: Veerle M
authors: VM
authors: Darras
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D002642:Chick Embryo; D002645:Chickens; D047108:Embryonic Development; D018507:Gene Expression Regulation, Developmental; D007453:Iodide Peroxidase / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D013961:Thyroid Gland / Q000196:embryology / Q000378:metabolism*; D013974:Thyroxine / Q000378:metabolism* / Q000494:pharmacology; D013997:Time Factors; D014284:Triiodothyronine / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D014284:Triiodothyronine; D007453:Iodide Peroxidase; D013974:Thyroxine