Inductive effect of ginsenoside-Rg1 on tyrosine aminotransferase gene expression in rat primary hepatocyte cultures.
Ginsenoside-Rg1 (G-Rg1) present in the roots of Panax ginseng (C. A. Meyer) has been shown to induce the enzyme activity of tyrosine aminotransferase (TAT) EC(2.6.1.5) in rat hepatocyte cultures. Thus, we investigated whether the inductive effect of G-Rg1 may act through glucocorticoid receptor- or cAMP-mediated action mechanism in the hepatocyte cultures. G-Rg1 induced the TAT activity by 2-fold with a similar time course to that of dexamethasone in the cell cultures. This effect of G-Rg1 was abolished to the basal level when RU486, a specific glucocorticoid antagonist was added to 10(-5)M. Furthermore, the additive effect of G-Rg1 and dexamethasone was inhibited as well by RU486. G-Rg1 and dibutyryl-cAMP (Bt2-cAMP) also revealed an additive effect but this additive effect was inhibited only to the G-Rg1-induced level by Rp-cAMPS, a specific inhibitor of protein kinase A. From these results, we suggest that the action mechanism of G-Rg1 leading to the induction of TAT activity may be mediated through glucocorticoid receptor binding and may not directly act through cAMP-mediated induction mechanism.
Kim
M Y
MY
College of Pharmacy, Seoul National University, Korea.
Lee
K Y
KY
Lee
S K
SK
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects*; D036145:Ginsenosides; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D008297:Male; D015735:Mifepristone / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D012503:Saponins / Q000494:pharmacology*; D014444:Tyrosine Transaminase / Q000037:antagonists & inhibitors / Q000235:genetics*
D036145:Ginsenosides; D011965:Receptors, Glucocorticoid; D012503:Saponins; D015735:Mifepristone; D003994:Bucladesine; D003907:Dexamethasone; D014444:Tyrosine Transaminase; C035054:ginsenoside Rg1