A comparison of thyrotropin- and dibutyryl cyclic AMP- induced thyroglobulin iodination in cultured human thyroid cells.
The relative degree of 125-I labelling of thyroglobulin-- bound mono-iodotyrosine (MIT) and di-iodotyrosine (DIT) in isolated, cultured human thyroid cells has been compared following exposure of 125-I supplemented cells to 100 mU/ml of bovine thyrotropin (TSH) or 1.0 mM dibutyryl cyclic AMP (dBcAMP) for 96 hours. Pronase digestion of the lysed cells and Sephadex G-10 fractionation of the digested lysates revealed a predominance of [125-I]MIT over [125-I]DIT in both sets of experimental cells as well as in controls. Levels of [125-I]DIT, however, were only enhanced above control values in cells incubated with TSH. These findings suggest that an increase in availability of intracellular iodide, following cellular exposure to TSH, may facilitate a preferential synthesis of DIT relative to that of MIT. This theory offers an explanation for the differential effects of TSH and dibutyryl cyclic AMP on the levels of newly--synthesised T4 recovered from the cells used in this study, and from the culture medium in a previous investigation.
Bidey
S P
SP
Department of Medicine, King's College Hospital Medical School, London SE5 8RX, England.
Marsden
P
P
Berry
H
H
Anderson
J
J
McKerron
C
C
D003994:Bucladesine / Q000494:pharmacology*; D002478:Cells, Cultured; D002850:Chromatography, Gel; D003911:Dextrans; D004105:Diiodotyrosine / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007455:Iodine / Q000378:metabolism*; D007470:Monoiodotyrosine / Q000737:chemistry / Q000378:metabolism; D013954:Thyroglobulin / Q000737:chemistry / Q000378:metabolism*; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*
D003911:Dextrans; D003994:Bucladesine; D004105:Diiodotyrosine; D013972:Thyrotropin; D013954:Thyroglobulin; C025614:sephadex; D007455:Iodine; D007470:Monoiodotyrosine