Ginsenoside-Rg1 regulates the induction of tyrosine aminotransferase gene transcription in rat hepatocyte cultures.
Ginsenosides present in the roots of Panax ginseng C.A. Meyer have been shown to induce a number of hepatocyte gene expression. We have recently demonstrated that ginsenoside-Rg1 (G-Rg1) stimulated the enzyme activity of tyrosine aminotransferase (TAT), a hepatocyte specific enzyme, of which enzyme activity was dose-dependently inhibited by RU486, a specific glucocorticoid antagonist. This study was therefore designed to determine whether G-Rg1 induces the transcriptional activity of TAT gene and to investigate whether G-Rg1 induces the gene transcription by glucocorticoid receptor- or cAMP-mediated induction mechanism. The slot blot hybridization analysis revealed that the TAT-mRNA level was increased by 9.3-fold in hepatocyte cultures in response to G-Rg1 stimulation. In contrast, the inductive effect of G-Rg1 was almost equally inhibited, that is, by 49% or 50% respectively in the presence of RU486 or Rp-cAMPs, a specific competitive inhibitor of protein kinase A. These results in hepatocyte cultures suggest that G-Rg1 modulates the TAT gene transcription through its influence on a functional or cooperative interaction between glucocorticoid receptor- and cAMP-mediated induction mechanism.
Kang
S Y
SY
College of Pharmacy, Seoul National University, Korea.
Lee
K Y
KY
Lee
S K
SK
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D017931:DNA Primers / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D036145:Ginsenosides; D008099:Liver / Q000187:drug effects* / Q000201:enzymology*; D015735:Mifepristone / Q000494:pharmacology; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D012503:Saponins / Q000494:pharmacology*; D013873:Thionucleotides / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014444:Tyrosine Transaminase / Q000235:genetics*
D017931:DNA Primers; D004365:Drugs, Chinese Herbal; D036145:Ginsenosides; D012333:RNA, Messenger; D012503:Saponins; D013873:Thionucleotides; C016957:adenosine-3',5'-cyclic phosphorothioate; D015735:Mifepristone; D003907:Dexamethasone; D000242:Cyclic AMP; D014444:Tyrosine Transaminase; D017868:Cyclic AMP-Dependent Protein Kinases; C035054:ginsenoside Rg1