title: Thyroxine-binding globulin and thyroxine-binding prealbumin in hypothyroid and hyperthyroid developing rats.
abstract: We present evidence based on equilibrium and non-equilibrium binding studies, as well as on immunological techniques, that of the two rat specific thyroid-hormone-binding proteins, i.e., thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA), TBG but not TBPA is regulated by the thyroid hormones (TH). Hypothyroidism, induced from the day of birth by daily treatment with propylthiouracil (PTU-rats), leads to dramatic and sustained increases of the TH-binding abilities of the sera measured at equilibrium, whereas hyperthyroidism, induced by treatment with thyroxine (T4-rats), leads to the decrease of these abilities. Polyacrylamide gel electrophoresis and isoelectrofocalisation of radioiodinated T4-labelled sera, together with immunoassay of TBPA, demonstrate that both effects are due to TBG, the levels of which rise in PTU-rats and decline in T4-rats, while TBPA levels do not respond to either depletion or excess of the thyroid hormones. TBG rather than TBPA appears as the key thyroid-hormone-binding protein of the rat, inasmuch as it alone expresses a regulatory function of the thyroid hormones at protein synthesis level.
authors.affiliation: Unité 224, INSERM affiliée au CNRS, Paris, France.
authors.forename: L
authors.initials: L
authors.lastname: Savu
authors.forename: R
authors.initials: R
authors.lastname: Vranckx
authors.forename: M
authors.initials: M
authors.lastname: Maya
authors.forename: D
authors.initials: D
authors.lastname: Gripois
authors.forename: M F
authors.initials: MF
authors.lastname: Blouquit
authors.forename: E A
authors.initials: EA
authors.lastname: Nunez
mesh_terms: D000375:Aging; D000818:Animals; D006980:Hyperthyroidism / Q000097:blood*; D007037:Hypothyroidism / Q000097:blood*; D007700:Kinetics; D011441:Propylthiouracil / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013974:Thyroxine / Q000097:blood; D013975:Thyroxine-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D014284:Triiodothyronine / Q000097:blood
chemical_list: D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine; D011441:Propylthiouracil; D013974:Thyroxine