ALTERATIONS OF ANTIOXIDANT ENZYME EXPRESSION IN RESPONSE TO HYDROGEN-PEROXIDE

The effect of hydrogen peroxide (H2O2) on the expression of different antioxidant enzymes was investigated in primary rat hepatocytes and th e rat hepatoma H4IIE cell line. Catalase mRNA expression and enzyme ac tivity decreased during rat hepatocyte culture. Exposure of hepatocyte s to H2O2 prevented this decrease in catalase mRNA expression, catalas e expression was induced 2-fold. MnSOD message levels showed a peak af ter 12 h of culture and MnSOD enzyme activity increased similarly. MnS OD mRNA expression was also induced after exposure to H2O2 Cu/ZnSOD mR NA expression remained constant during culturing and was not affected by H2O2 treatment. In confluent hepatoma H4IIE cells catalase mRNA exp ression was lower than in early hepatocyte cultures and could be induc ed 2-fold upon treatment with H2O2. Actinomycin D alone caused the sam e amount of induction of catalase mRNA in rat hepatocytes as in combin ation with H2O2 Exposure of hepatocytes to cycloheximide did not influ ence the induction of catalase mRNA by H2O2. In rat hepatoma H4IIE cel ls the induction of catalase mRNA by H2O2 was prevented by the additio n of actinomycin D or cycloheximide. Although induction of catalase mR NA by H2O2 was found in rat hepatocytes and H4IIE cells, gene expressi on of catalase does not appear to be regulated in both cell types in t he same manner. (C) 1997 Elsevier Science Inc.