Thyroid hormone transport in a human glioma cell line.
The uptake of 3,5,3'-triiodothyronine (T3) and thyroxine (T4) was studied in human glioma cells (Hs 683) and compared with that in several other neural cell lines. At 25 degrees C or 37 degrees C, total cell uptake rose rapidly and reached equilibrium within 60 min. The glioma cells had the highest uptake: 47.6 fmol of L-T3 and 43.4 fmol of L-T4 per 10(6) cells at 37 degrees C. These were inhibited 77% and 72%, respectively, by excess unlabeled hormone. Uptake in the nuclei reached equilibrium between 90 and 120 min and was also highest in glioma cells: 1.46 fmol of L-T3 and 0.49 fmol of L-T4 per 10(6) cells. When expressed as percent of total cell uptake, however, glioma cells had the lowest values (3.1% for L-T3 and 1.1% for L-T4). Also in contrast to other cell lines, glioma cells transported L-T4 almost as effectively as L-T3. D-T3 and D-T4 total cell uptake was 86% and 96% lower than that of the respective L-isomers, and the nuclear uptake as a fraction of the cell uptake was similar. Kinetic analysis of the initial rate of cell uptake gave Vmax values for D-T3 and D-T4 that were 97% and 98% lower than for the L-isomers. Antimycin and monodansylcadaverine decreased the Vmax as well as the equilibrium cell and nuclear uptake of the L-isomers. The apparent nuclear affinity constant for L-T4 in intact cells was inhibited 90% in the presence of antimycin, whereas no effect was observed in isolated nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)
Goncalves
E
E
Clinical Endocrinology Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Lakshmanan
M
M
Pontecorvi
A
A
Robbins
J
J
D000621:Aminoisobutyric Acids / Q000494:pharmacology; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008527:Medulloblastoma / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D013696:Temperature; D013974:Thyroxine / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000621:Aminoisobutyric Acids; D014284:Triiodothyronine; C032456:antimycin; C100049:2-aminoisobutyric acid; D010042:Ouabain; D000968:Antimycin A; C008542:monodansylcadaverine; D002103:Cadaverine; D013974:Thyroxine