Changes in expression and de novo synthesis of GST subunits in cultured adult rat hepatocytes.

Glutathione S-transferase (GST) isoenzymes of conventionally and co-cultured adult rat hepatocytes were purified and the GST subunits were separated by reversed phase HPLC in order to study the development of the GST subunit composition as a function of culture time and culture conditions. Several media conditions were tested, namely medium with and without fetal calf serum and with nicotinamide or dimethyl sulphoxide. Compared to the GST subunit composition of freshly isolated hepatocytes, changes in culture and media conditions result in a modification of the subunit profile. General observations are a decrease of subunits 1 and 2, an increase of subunit 3, a stabilization of subunit 4 and "de novo" expression of subunit 7. When [35S] methionine was added to the various culture media, and the thus labelled subunits were purified and separated, it was shown that cultured adult rat hepatocytes are able to synthesize the different GST proteins. Furthermore, the GST subunit composition, measured during various culture conditions, is probably a reflection of the "de novo" synthesis in vitro.