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Thyroid Hormone Receptors and Stimulation of Angiotensinogen Production in HepG2 Cells

Ian A. Darby, Jacob Bouhnik, Ericque D. Coezy and Pierre Corvol
In Vitro Cellular & Developmental Biology
Vol. 27A, No. 1 (Jan., 1991), pp. 21-24
Stable URL: http://www.jstor.org/stable/4296599
Page Count: 4
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Thyroid Hormone Receptors and Stimulation of Angiotensinogen Production in HepG2 Cells
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Abstract

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 $[^{125}I]T_3$. 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 $[^{125}I]T_3$ 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 $5.0 \times 10^{-8}$ mol/liter. T3 also produced after 24 h a dose-dependent increase in DNA highly correlated with T3 applied (r = 0.88, P < 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.

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