GINSENOSIDE-RG(1) 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-Rg(1) (G-Rg(1)) 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-Rg(1) induces the transcriptional activity of TAT gene and to investigate whether G-Rg(1) 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-Rg(1) stimulation. In contrast, the inductive effect of G-Rg(1) 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-Rg(1) modulates the TAT gene transcription through its influence on a functional or cooperative interaction between glucocorticoid receptor- and cAMP-mediated induction mechanism. (C) 1994 Academic Press, Inc.