PHENOBARBITAL PREVENTS THE INHIBITORY EFFECTS OF TUMOR-NECROSIS-FACTOR ON GLUTATHIONE-S-TRANSFERASE-MU IN PRIMARY CULTURE RAT HEPATOCYTES

During inflammation and infection, overexpression of the tumor necrosi s factor (TNF) is associated with changes in cytochromes P-450 levels in rat and human hepatocytes. The aim of this study was to investigate the effect of TNF on the expression of the glutathione-S-transferases (GSTs) in rat hepatocytes. TNF was added in vitro alone or simultaneo usly with phenobarbital (PB) into hepatocytes in primary culture or in vivo, before TNF, injected directly to rats. GST activity was assayed by spectrophotometry; protein GSTs alpha, mu and pi were evaluated by immunoblotting. When TNF was added alone to rat hepatocytes in vitro, fetal GST activity and GST alpha levels were not affected, while GST mu protein levels significantly decreased by 35%. GST pi protein was u ndetectable in hepatocytes whether treated or not with TNF. When PB wa s administered in vitro simultaneously to rat hepatocytes with TNF, th e decrease observed for GST mu subunit was suppressed while total GST activity and GST alpha content were not affected When hepatocytes were ,treated with TNF after PB given in vivo directly to the rat by ip inj ection, GST activity and GSTs subunits were induced by PB, while TNF d id not exert any effect These results indicate that TNF has an inhibit ory effect on GST mu and PB abrogates this effect in primary cultured vat hepatocytes. Then, PB could prevent some TNF toxic effects.