title: The metabolism of T4 and T3 in cultured chick-embryo heart cells.
abstract: Thyroxine (T4) and tri-iodothyronine (T3) were metabolized in cultured chick-embryo heart cells via inner-ring de-iodination and O-sulfation. The products of T3 metabolism were 3,3'T2, 3'T1, and sulfated esters of T3 and 3,3'T2. The major product of T4 degradation was 3,3',5'-T3 (rT3). ONo T3 was produced from T4. Propylthioracil inhibited the metabolism of T3. Pretreatment of cultures with T3 or T4 enhanced the metabolism of both hormones; actinomycin D and cycloheximide inhibited the stimulatory effect of T3. The stimulation by T3 was linearly related to the log of the concentration of T3 in cells grown in normal chick serum or in cells grown in dehormonized serum. These results suggest that thyroid hormones induced an increased synthesis of the enzymes involved in their metabolism and therefore may regulate their own disposal rate.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D011441:Propylthiouracil / Q000494:pharmacology; D013974:Thyroxine / Q000378:metabolism* / Q000494:pharmacology; D014284:Triiodothyronine / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D014284:Triiodothyronine; D003609:Dactinomycin; D011441:Propylthiouracil; D003513:Cycloheximide; D013974:Thyroxine