Proteins but not nucleic acids are molecular targets for the free radical attack during reoxygenation of rat hepatocytes.

Isolated rat hepatocytes generate large amounts of reactive oxygen species and suffer a significant cell injury during postanoxic reoxygenation. The aim of this study was to determine whether oxidation of proteins and nucleic acids occurs during reoxygenation and whether their damage is related to the development of hepatocyte injury. Isolated perfused rat hepatocytes were exposed sequentially to 1 h of aerobic control, 2.5 h of anoxia, and 2 h of reoxygenation. Protein oxidation was determined by measuring the hepatocyte protein carbonyl content. DNA and RNA oxidation was assessed by measuring the 8-hydroxydeoxyguanosine and 8-hydroxyguanosine adducts, respectively. The control preanoxic carbonyl content was 6.48 +/- 1.03 nmol/mg protein. The preanoxic 8-8 hydroxydeoxyguanosine and 8-hydroxyguanosine levels were 4.76 +/- 1.22 pmol/ml and 14.19 +/- 2.17 pmol/ml, respectively. During anoxia, protein and nucleic acid oxidation did not change significantly. With reoxygenation, the protein carbonyl content increased significantly within 30 min, reaching a value of 10.25 +/- 1.58 nmol/mg. The nucleic acid oxidation level remained stable. Perfusion with 100 muM of during reoxygenation abolished protein oxidation. These results indicate that in rat hepatocytes during the early phase of reoxygenation: (1) the protein oxidation level increased significantly above the preanoxic aerobic values; (2) DNA and RNA oxidation does not appear to occur; and (3) free metal-mediated free radical reactions are involved in the oxidative protein damage.