Actions of 3,5,3'-tri-iodothyronine on the synthesis and secretion of major plasma proteins by a human hepatoblastoma cell line (Hep G2).
We have elucidated the action of tri-iodothyronine (T3) on the synthesis and secretion of seven major plasma proteins in a human hepatoblastoma cell line, Hep G2, and established an in vitro experimental model of human liver cells for the study of the mechanism of the action of thyroid hormone. Hep G2 cells cultured in serum-free medium were treated with various concentrations of T3. During the first 24 h of T3 treatment, accumulation of alpha-fetoprotein in the medium was decreased in a dose-dependent manner (10(-11)-10(-8) M), and the inhibitory effect was enhanced during the second 24 h of T3 treatment. On the other hand, alpha 1-antitrypsin accumulation in the medium during the second 24 h of hormone treatment was decreased by T3 (10(-9)-10(-8) M), although no change in accumulation was observed during the first 24 h of T3 treatment. The newly synthesized [35S]Met-labelled alpha 1-acid glycoprotein was increased by T3 and reached 3.4-fold within 37 h of 10(-8) M T3 treatment. The stimulatory effect increased time-dependently (4.6-fold after 61 h). In contrast, the synthesis of alpha-fetoprotein was reduced to half of that of the control after T3 treatment for 37 h. Although the content of newly synthesized [35S]alpha 1-antitrypsin was not affected by 10(-8) M T3 treatment during 3 days of hormone treatment, the accumulation of alpha 1-antitrypsin in the medium decreased to 87%; in contrast, total cellular newly synthesized alpha 1-antitrypsin increased to 105-130% of that of the control.(ABSTRACT TRUNCATED AT 250 WORDS)
Kobayashi
M
M
Institute of Endocrinology, Gunma University, Maebashi, Japan.
Horiuchi
R
R
D000209:Acute-Phase Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D016895:Culture Media, Serum-Free; D015180:Electrophoresis, Gel, Two-Dimensional; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D007700:Kinetics; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D014284:Triiodothyronine / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000209:Acute-Phase Proteins; D016895:Culture Media, Serum-Free; D009363:Neoplasm Proteins; D014284:Triiodothyronine