Thyroid hormone receptors and stimulation of angiotensinogen production in HepG2 cells.
Binding characteristics and effects of 3,5,-3'-triiodo-L-thyronine (T3) on angiotensinogen production in HepG2 were studied in serum-free medium. Binding was performed on intact cells and on partially purified isolated nuclei using [125I]T3. Scatchard plots revealed one class of high affinity binding sites with a Kd of approximately 80 pmol/liter. Calculation of maximum binding showed that HepG2 possess approximately 1000 binding sites per cell. Unlabeled T3 and T4 competed for binding sites on intact HepG2 with 50% inhibition of [125I] T3 binding at approximately 3.0 and 38.0 pmol/liter, respectively. The HepG2 showed a dose-dependent increase in angiotensinogen production in serum-free medium which was maximal at 10(-5) mol/liter (two-fold increase/10(6) cells/24 h) and had an EC50 of approximately 5.0 x 10(-8) mol/liter. T3 also produced after 24 h a dose-dependent increase in DNA highly correlated with T3 applied (r = 0.88, P less than 0.01). In conclusion, this study shows that HepG2 possess specific high affinity binding sites for T3 and that T3 stimulates angiotensinogen production and DNA synthesis in these cells.
Darby
I A
IA
INSERM Unit 36, Paris, France.
Bouhnik
J
J
Coezy
E D
ED
Corvol
P
P
D000808:Angiotensinogen / Q000096:biosynthesis*; D001667:Binding, Competitive; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008113:Liver Neoplasms; D011988:Receptors, Thyroid Hormone / Q000187:drug effects / Q000502:physiology*; D013974:Thyroxine / Q000494:pharmacology*; D014284:Triiodothyronine / Q000378:metabolism / Q000494:pharmacology*
D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine; D000808:Angiotensinogen; D013974:Thyroxine