Transcriptional- and post-transcriptional-dependent regulation of glutathione S-transferase expression in rat hepatocytes as a function of culture conditions.
Transcriptional activity of the glutathione S-transferase (GST) alpha (subunits 1 and 2), mu (subunits 3 and 4) and pi (subunit 7) gene families has been analyzed using the nuclear 'run-on' technique on adult rat hepatocytes maintained for 4 days in conventional culture and for 4 and 12 days in co-culture with rat liver epithelial cells. Several medium conditions are included in this study, namely with or without fetal calf serum and with nicotinamide or dimethylsulphoxide. Hepatocytes co-cultured for 4 days maintain approximately 30-70% of the alpha gene family transcriptional activity, whatever the medium conditions, when compared to freshly isolated hepatocytes. A marked decrease is observed after 12 days of co-culture or when hepatocytes are maintained in conventional culture. The transcriptional activity of the mu gene family is maintained at 40-160% when hepatocytes are cultured with or without fetal calf serum, and is inducible by nicotinamide (approximately 4-fold) and dimethylsulphoxide (approximately 2-fold) in conventional culture and/or in co-culture. In contrast to freshly isolated hepatocytes, GST pi gene transcriptional activity is observed in conventional and co-cultured hepatocytes, irrespective of the medium conditions. Dimethylsulphoxide treatment however, represses the expression of GST 7 in vitro. These results demonstrate that the expression of GST alpha, mu and pi genes in conventional and co-cultured rat hepatocytes is controlled primarily at the level of transcription. It cannot be excluded, however, that dimethylsulphoxide stabilizes the GST mRNA levels in vitro.
Vandenberghe
Y
Y
Department of Toxicology, Vrije Universiteit Brussel, Belgium.
Tee
L
L
Rogiers
V
V
Yeoh
G
G
D000818:Animals; D002478:Cells, Cultured; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D005982:Glutathione Transferase / Q000235:genetics*; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014158:Transcription, Genetic
D005982:Glutathione Transferase; D004121:Dimethyl Sulfoxide